/src/git/graph.c

Source
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "gettext.h"
#include "config.h"
#include "commit.h"
#include "color.h"
#include "graph.h"
#include "revision.h"
#include "strvec.h"

/* Internal API */

/*
 * Output a padding line in the graph.
 * This is similar to graph_next_line().  However, it is guaranteed to
 * never print the current commit line.  Instead, if the commit line is
 * next, it will simply output a line of vertical padding, extending the
 * branch lines downwards, but leaving them otherwise unchanged.
 */
static void graph_padding_line(struct git_graph *graph, struct strbuf *sb);

/*
 * Print a strbuf.  If the graph is non-NULL, all lines but the first will be
 * prefixed with the graph output.
 *
 * If the strbuf ends with a newline, the output will end after this
 * newline.  A new graph line will not be printed after the final newline.
 * If the strbuf is empty, no output will be printed.
 *
 * Since the first line will not include the graph output, the caller is
 * responsible for printing this line's graph (perhaps via
 * graph_show_commit() or graph_show_oneline()) before calling
 * graph_show_strbuf().
 *
 * Note that unlike some other graph display functions, you must pass the file
 * handle directly. It is assumed that this is the same file handle as the
 * file specified by the graph diff options. This is necessary so that
 * graph_show_strbuf can be called even with a NULL graph.
 * If a NULL graph is supplied, the strbuf is printed as-is.
 */
static void graph_show_strbuf(struct git_graph *graph,
            FILE *file,
            struct strbuf const *sb);

/*
 * TODO:
 * - Limit the number of columns, similar to the way gitk does.
 *   If we reach more than a specified number of columns, omit
 *   sections of some columns.
 */

struct column {
  /*
   * The parent commit of this column.
   */
  struct commit *commit;
  /*
   * The color to (optionally) print this column in.  This is an
   * index into column_colors.
   */
  unsigned short color;
  /*
   * Marks if a commit is a non-first parent of a merge. These columns are
   * already visually connected to the merge commit and do not need
   * indentation.
   *
   * The first parent is the one that inherits the column and it can need
   * indentation if turns out to be a visual root and there's still
   * commits to render.
   */
  unsigned int is_merge_parent:1;
};

enum graph_state {
  GRAPH_PADDING,
  GRAPH_SKIP,
  GRAPH_PRE_COMMIT,
  GRAPH_PRE_ROOT,
  GRAPH_COMMIT,
  GRAPH_POST_MERGE,
  GRAPH_COLLAPSING
};

static void graph_show_line_prefix(const struct diff_options *diffopt)
{
  if (!diffopt || !diffopt->line_prefix)
    return;

  fputs(diffopt->line_prefix, diffopt->file);
}

static const char **column_colors;
static unsigned short column_colors_max;

static void parse_graph_colors_config(struct strvec *colors, const char *string)
{
  const char *end, *start;

  start = string;
  end = string + strlen(string);
  while (start < end) {
    const char *comma = strchrnul(start, ',');
    char color[COLOR_MAXLEN];

    if (!color_parse_mem(start, comma - start, color))
      strvec_push(colors, color);
    else
      warning(_("ignored invalid color '%.*s' in log.graphColors"),
        (int)(comma - start), start);
    start = comma + 1;
  }
  strvec_push(colors, GIT_COLOR_RESET);
}

void graph_set_column_colors(const char **colors, unsigned short colors_max)
{
  column_colors = colors;
  column_colors_max = colors_max;
}

static const char *column_get_color_code(unsigned short color)
{
  return column_colors[color];
}

struct graph_line {
  struct strbuf *buf;
  size_t width;
};

static inline void graph_line_addch(struct graph_line *line, int c)
{
  strbuf_addch(line->buf, c);
  line->width++;
}

static inline void graph_line_addchars(struct graph_line *line, int c, size_t n)
{
  strbuf_addchars(line->buf, c, n);
  line->width += n;
}

static inline void graph_line_addstr(struct graph_line *line, const char *s)
{
  strbuf_addstr(line->buf, s);
  line->width += strlen(s);
}

static inline void graph_line_addcolor(struct graph_line *line, unsigned short color)
{
  strbuf_addstr(line->buf, column_get_color_code(color));
}

static void graph_line_write_column(struct graph_line *line, const struct column *c,
            char col_char)
{
  if (c->color < column_colors_max)
    graph_line_addcolor(line, c->color);
  graph_line_addch(line, col_char);
  if (c->color < column_colors_max)
    graph_line_addcolor(line, column_colors_max);
}

struct git_graph {
  /*
   * The commit currently being processed
   */
  struct commit *commit;
  /* The rev-info used for the current traversal */
  struct rev_info *revs;
  /*
   * The number of interesting parents that this commit has.
   *
   * Note that this is not the same as the actual number of parents.
   * This count excludes parents that won't be printed in the graph
   * output, as determined by graph_is_interesting().
   */
  int num_parents;
  /*
   * The width of the graph output for this commit.
   * All rows for this commit are padded to this width, so that
   * messages printed after the graph output are aligned.
   */
  int width;
  /*
   * The next expansion row to print
   * when state is GRAPH_PRE_COMMIT
   */
  int expansion_row;
  /*
   * The current output state.
   * This tells us what kind of line graph_next_line() should output.
   */
  enum graph_state state;
  /*
   * The output state for the previous line of output.
   * This is primarily used to determine how the first merge line
   * should appear, based on the last line of the previous commit.
   */
  enum graph_state prev_state;
  /*
   * The index of the column that refers to this commit.
   *
   * If none of the incoming columns refer to this commit,
   * this will be equal to num_columns.
   */
  int commit_index;
  /*
   * The commit_index for the previously displayed commit.
   *
   * This is used to determine how the first line of a merge
   * graph output should appear, based on the last line of the
   * previous commit.
   */
  int prev_commit_index;
  /*
   * Which layout variant to use to display merge commits. If the
   * commit's first parent is known to be in a column to the left of the
   * merge, then this value is 0 and we use the layout on the left.
   * Otherwise, the value is 1 and the layout on the right is used. This
   * field tells us how many columns the first parent occupies.
   *
   *    0)      1)
   *
   *    | | | *-.   | | *---.
   *    | |_|/|\ \    | | |\ \ \
   *    |/| | | | |   | | | | | *
   */
  int merge_layout;
  /*
   * The number of columns added to the graph by the current commit. For
   * 2-way and octopus merges, this is usually one less than the
   * number of parents:
   *
   *    | | |     | |    \
   *    | * |     | *---. \
   *    | |\ \      | |\ \ \ \
   *    | | | |           | | | | | |
   *
   *    num_parents: 2    num_parents: 4
   *    edges_added: 1    edges_added: 3
   *
   * For left-skewed merges, the first parent fuses with its neighbor and
   * so one less column is added:
   *
   *    | | |     | |  \
   *    | * |     | *-. \
   *    |/| |     |/|\ \ \
   *    | | |     | | | | |
   *
   *    num_parents: 2    num_parents: 4
   *    edges_added: 0    edges_added: 2
   *
   * This number determines how edges to the right of the merge are
   * displayed in commit and post-merge lines; if no columns have been
   * added then a vertical line should be used where a right-tracking
   * line would otherwise be used.
   *
   *    | * \     | * |
   *    | |\ \      |/| |
   *    | | * \     | * |
   */
  int edges_added;
  /*
   * The number of columns added by the previous commit, which is used to
   * smooth edges appearing to the right of a commit in a commit line
   * following a post-merge line.
   */
  int prev_edges_added;
  /*
   * The maximum number of columns that can be stored in the columns
   * and new_columns arrays.  This is also half the number of entries
   * that can be stored in the mapping and old_mapping arrays.
   */
  int column_capacity;
  /*
   * The number of columns (also called "branch lines" in some places)
   */
  int num_columns;
  /*
   * The number of columns in the new_columns array
   */
  int num_new_columns;
  /*
   * The number of entries in the mapping array
   */
  int mapping_size;
  /*
   * The column state before we output the current commit.
   */
  struct column *columns;
  /*
   * The new column state after we output the current commit.
   * Only valid when state is GRAPH_COLLAPSING.
   */
  struct column *new_columns;
  /*
   * An array that tracks the current state of each
   * character in the output line during state GRAPH_COLLAPSING.
   * Each entry is -1 if this character is empty, or a non-negative
   * integer if the character contains a branch line.  The value of
   * the integer indicates the target position for this branch line.
   * (I.e., this array maps the current column positions to their
   * desired positions.)
   *
   * The maximum capacity of this array is always
   * sizeof(int) * 2 * column_capacity.
   */
  int *mapping;
  /*
   * A copy of the contents of the mapping array from the last commit,
   * which we use to improve the display of columns that are tracking
   * from right to left through a commit line.  We also use this to
   * avoid allocating a fresh array when we compute the next mapping.
   */
  int *old_mapping;
  /*
   * The current default column color being used.  This is
   * stored as an index into the array column_colors.
   */
  unsigned short default_column_color;

  /*
   * Scratch buffer for generating prefixes to be used with
   * diff_output_prefix_callback().
   */
  struct strbuf prefix_buf;

  /*
   * Lookahead buffer: up to 2 pre-fetched commits that will be shown.
   * Populated by get_revision() so graph_peek_next_visible() can use
   * actual walk results instead of peeking at rev_info internals.
   */
  struct commit *lookahead[2];
  int lookahead_nr;

  /*
   * If a commit is a visual root, we need to indent it to prevent
   * unrelated commits from being vertically adjacent to it.
   */
  unsigned int is_visual_root:1;

  /*
   * Indentation increases for each visual root adjacent to another visual
   * root, making visual root commits indentation cascade.
   */
  unsigned int visual_root_depth;

  /*
   * When a visual root is adjacent to other visual roots, the first one
   * can avoid indentation and the rest cascades, increasing the indentation
   * for each one.
   */
  unsigned int visual_root_cascade:1;

  /*
   * Set when the current commit was already present in graph->columns
   * before being processed.
   */
  unsigned int commit_in_columns:1;
};

struct graph_lookahead_flags {

  /*
   * Set when there will be a commit after the current one that will be
   * rendered.
   */
  unsigned int is_next_visible:1;

  /*
   * Set when the next visible commit is candidate to be a visual root.
   */
  unsigned int is_next_visual_root:1;

  /*
   * Set when the next visible commit will be rendered under the current
   * commit.
   */
  unsigned int next_has_column:1;
};

static inline int graph_needs_truncation(struct git_graph *graph, int lane)
{
  int max = graph->revs->graph_max_lanes;
  /*
   * Ignore values <= 0, meaning no limit.
   */
  return max > 0 && lane >= max;
}

static const char *diff_output_prefix_callback(struct diff_options *opt, void *data)
{
  struct git_graph *graph = data;

  assert(opt);

  if (!graph)
    return opt->line_prefix;

  strbuf_reset(&graph->prefix_buf);
  if (opt->line_prefix)
    strbuf_addstr(&graph->prefix_buf, opt->line_prefix);
  graph_padding_line(graph, &graph->prefix_buf);
  return graph->prefix_buf.buf;
}

static const struct diff_options *default_diffopt;

void graph_setup_line_prefix(struct diff_options *diffopt)
{
  default_diffopt = diffopt;

  /* setup an output prefix callback if necessary */
  if (diffopt && !diffopt->output_prefix)
    diffopt->output_prefix = diff_output_prefix_callback;
}

static void graph_read_config(struct rev_info *revs)
{
  int val;

  if (!column_colors) {
    char *string;
    if (repo_config_get_string(revs->repo, "log.graphcolors", &string)) {
      /* not configured -- use default */
      graph_set_column_colors(column_colors_ansi,
            column_colors_ansi_max);
    } else {
      static struct strvec custom_colors = STRVEC_INIT;
      strvec_clear(&custom_colors);
      parse_graph_colors_config(&custom_colors, string);
      free(string);
      /* graph_set_column_colors takes a max-index, not a count */
      graph_set_column_colors(custom_colors.v,
            custom_colors.nr - 1);
    }
  }

  if (!repo_config_get_bool(revs->repo, "log.graphIndent", &val))
    revs->no_graph_indent = !val;
}

struct git_graph *graph_init(struct rev_info *opt)
{
  struct git_graph *graph = xmalloc(sizeof(struct git_graph));

  graph_read_config(opt);

  graph->commit = NULL;
  graph->revs = opt;
  graph->num_parents = 0;
  graph->expansion_row = 0;
  graph->state = GRAPH_PADDING;
  graph->prev_state = GRAPH_PADDING;
  graph->commit_index = 0;
  graph->prev_commit_index = 0;
  graph->merge_layout = 0;
  graph->edges_added = 0;
  graph->prev_edges_added = 0;
  graph->num_columns = 0;
  graph->num_new_columns = 0;
  graph->mapping_size = 0;
  graph->lookahead[0] = NULL;
  graph->lookahead[1] = NULL;
  graph->lookahead_nr = 0;
  graph->visual_root_depth = 0;
  graph->visual_root_cascade = 0;
  /*
   * Start the column color at the maximum value, since we'll
   * always increment it for the first commit we output.
   * This way we start at 0 for the first commit.
   */
  graph->default_column_color = column_colors_max - 1;

  /*
   * Allocate a reasonably large default number of columns
   * We'll automatically grow columns later if we need more room.
   */
  graph->column_capacity = 30;
  ALLOC_ARRAY(graph->columns, graph->column_capacity);
  ALLOC_ARRAY(graph->new_columns, graph->column_capacity);
  ALLOC_ARRAY(graph->mapping, 2 * graph->column_capacity);
  ALLOC_ARRAY(graph->old_mapping, 2 * graph->column_capacity);

  /*
   * The diff output prefix callback, with this we can make
   * all the diff output to align with the graph lines.
   */
  strbuf_init(&graph->prefix_buf, 0);
  opt->diffopt.output_prefix = diff_output_prefix_callback;
  opt->diffopt.output_prefix_data = graph;

  return graph;
}

void graph_clear(struct git_graph *graph)
{
  if (!graph)
    return;

  free(graph->columns);
  free(graph->new_columns);
  free(graph->mapping);
  free(graph->old_mapping);
  strbuf_release(&graph->prefix_buf);
  free(graph);
}

static void graph_update_state(struct git_graph *graph, enum graph_state s)
{
  graph->prev_state = graph->state;
  graph->state = s;
}

static void graph_ensure_capacity(struct git_graph *graph, int num_columns)
{
  if (graph->column_capacity >= num_columns)
    return;

  do {
    graph->column_capacity *= 2;
  } while (graph->column_capacity < num_columns);

  REALLOC_ARRAY(graph->columns, graph->column_capacity);
  REALLOC_ARRAY(graph->new_columns, graph->column_capacity);
  REALLOC_ARRAY(graph->mapping, graph->column_capacity * 2);
  REALLOC_ARRAY(graph->old_mapping, graph->column_capacity * 2);
}

/*
 * Returns 1 if the commit will be printed in the graph output,
 * and 0 otherwise.
 */
static int graph_is_interesting(struct git_graph *graph, struct commit *commit)
{
  /*
   * Commits in the lookahead buffer have been pre-fetched by
   * get_revision() and will be shown in the future. They already have
   * the SHOWN flag set when they were pre-fetched but the graph still
   * needs to treat them as interesting parents.
   */
  for (int i = 0; i < graph->lookahead_nr; i++)
    if (graph->lookahead[i] == commit)
      return 1;
  /*
   * If revs->boundary is set, commits whose children have
   * been shown are always interesting, even if they have the
   * UNINTERESTING or TREESAME flags set.
   */
  if (graph->revs && graph->revs->boundary) {
    if (commit->object.flags & CHILD_SHOWN)
      return 1;
  }

  /*
   * Otherwise, use get_commit_action() to see if this commit is
   * interesting
   */
  return get_commit_action(graph->revs, commit) == commit_show;
}

static struct commit_list *next_interesting_parent(struct git_graph *graph,
               struct commit_list *orig)
{
  struct commit_list *list;

  /*
   * If revs->first_parent_only is set, only the first
   * parent is interesting.  None of the others are.
   */
  if (graph->revs->first_parent_only)
    return NULL;

  /*
   * Return the next interesting commit after orig
   */
  for (list = orig->next; list; list = list->next) {
    if (graph_is_interesting(graph, list->item))
      return list;
  }

  return NULL;
}

static struct commit_list *first_interesting_parent(struct git_graph *graph)
{
  struct commit_list *parents = graph->commit->parents;

  /*
   * If this commit has no parents, ignore it
   */
  if (!parents)
    return NULL;

  /*
   * If the first parent is interesting, return it
   */
  if (graph_is_interesting(graph, parents->item))
    return parents;

  /*
   * Otherwise, call next_interesting_parent() to get
   * the next interesting parent
   */
  return next_interesting_parent(graph, parents);
}

static unsigned short graph_get_current_column_color(const struct git_graph *graph)
{
  if (!want_color(graph->revs->diffopt.use_color))
    return column_colors_max;
  return graph->default_column_color;
}

/*
 * Update the graph's default column color.
 */
static void graph_increment_column_color(struct git_graph *graph)
{
  graph->default_column_color = (graph->default_column_color + 1) %
    column_colors_max;
}

static unsigned short graph_find_commit_color(const struct git_graph *graph,
                const struct commit *commit)
{
  int i;
  for (i = 0; i < graph->num_columns; i++) {
    if (graph->columns[i].commit == commit)
      return graph->columns[i].color;
  }
  return graph_get_current_column_color(graph);
}

static int graph_find_new_column_by_commit(struct git_graph *graph,
             struct commit *commit)
{
  int i;
  for (i = 0; i < graph->num_new_columns; i++) {
    if (graph->new_columns[i].commit == commit)
      return i;
  }
  return -1;
}

static void graph_insert_into_new_columns(struct git_graph *graph,
            struct commit *commit,
            int idx)
{
  /*
   * Get the initial merge_layout before it's modified to know if this
   * is a merge.
   */
  int initial_merge_layout = graph->merge_layout;
  int i = graph_find_new_column_by_commit(graph, commit);
  int mapping_idx;

  /*
   * If the commit is not already in the new_columns array, then add it
   * and record it as being in the final column.
   */
  if (i < 0) {
    i = graph->num_new_columns++;
    graph->new_columns[i].commit = commit;
    graph->new_columns[i].color = graph_find_commit_color(graph, commit);
    graph->new_columns[i].is_merge_parent = 0;
  }

  if (graph->num_parents > 1 && idx > -1 && graph->merge_layout == -1) {
    /*
     * If this is the first parent of a merge, choose a layout for
     * the merge line based on whether the parent appears in a
     * column to the left of the merge
     */
    int dist, shift;

    dist = idx - i;
    shift = (dist > 1) ? 2 * dist - 3 : 1;

    graph->merge_layout = (dist > 0) ? 0 : 1;
    graph->edges_added = graph->num_parents + graph->merge_layout  - 2;

    mapping_idx = graph->width + (graph->merge_layout - 1) * shift;
    graph->width += 2 * graph->merge_layout;

  } else if (graph->edges_added > 0 && i == graph->mapping[graph->width - 2]) {
    /*
     * If some columns have been added by a merge, but this commit
     * was found in the last existing column, then adjust the
     * numbers so that the two edges immediately join, i.e.:
     *
     *    * |   * |
     *    |\ \  =>  |\|
     *    | |/    | *
     *    | *
     */
    mapping_idx = graph->width - 2;
    graph->edges_added = -1;
  } else {
    mapping_idx = graph->width;
    graph->width += 2;
  }

  graph->mapping[mapping_idx] = i;

  /*
   * Mark non-first parents of a merge.
   */
  if (graph->num_parents > 1 && initial_merge_layout >= 0 && idx > -1)
    graph->new_columns[i].is_merge_parent = 1;
}

static void graph_update_columns(struct git_graph *graph)
{
  struct commit_list *parent;
  int max_new_columns;
  int i, seen_this, is_commit_in_columns;

  /*
   * Swap graph->columns with graph->new_columns
   * graph->columns contains the state for the previous commit,
   * and new_columns now contains the state for our commit.
   *
   * We'll re-use the old columns array as storage to compute the new
   * columns list for the commit after this one.
   */
  SWAP(graph->columns, graph->new_columns);
  graph->num_columns = graph->num_new_columns;
  graph->num_new_columns = 0;

  /*
   * Now update new_columns and mapping with the information for the
   * commit after this one.
   *
   * First, make sure we have enough room.  At most, there will
   * be graph->num_columns + graph->num_parents columns for the next
   * commit.
   */
  max_new_columns = graph->num_columns + graph->num_parents;
  graph_ensure_capacity(graph, max_new_columns);

  /*
   * Clear out graph->mapping
   */
  graph->mapping_size = 2 * max_new_columns;
  for (i = 0; i < graph->mapping_size; i++)
    graph->mapping[i] = -1;

  graph->width = 0;
  graph->prev_edges_added = graph->edges_added;
  graph->edges_added = 0;

  /*
   * Populate graph->new_columns and graph->mapping
   *
   * Some of the parents of this commit may already be in
   * graph->columns.  If so, graph->new_columns should only contain a
   * single entry for each such commit.  graph->mapping should
   * contain information about where each current branch line is
   * supposed to end up after the collapsing is performed.
   */
  seen_this = 0;
  is_commit_in_columns = 1;
  for (i = 0; i <= graph->num_columns; i++) {
    struct commit *col_commit;
    if (i == graph->num_columns) {
      if (seen_this)
        break;
      is_commit_in_columns = 0;
      col_commit = graph->commit;
    } else {
      col_commit = graph->columns[i].commit;
    }

    if (col_commit == graph->commit) {
      seen_this = 1;
      graph->commit_index = i;
      graph->merge_layout = -1;
      for (parent = first_interesting_parent(graph);
           parent;
           parent = next_interesting_parent(graph, parent)) {
        /*
         * If this is a merge, or the start of a new
         * childless column, increment the current
         * color.
         */
        if (graph->num_parents > 1 ||
            !is_commit_in_columns) {
          graph_increment_column_color(graph);
        }
        graph_insert_into_new_columns(graph, parent->item, i);
      }
      /*
       * We always need to increment graph->width by at
       * least 2, even if it has no interesting parents.
       * The current commit always takes up at least 2
       * spaces.
       */
      if (graph->num_parents == 0)
        graph->width += 2;
    } else {
      int j;
      graph_insert_into_new_columns(graph, col_commit, -1);
      /*
       * This column is not the current commit, but we need to
       * propagate the flag until the commit is processed.
       */
      j = graph_find_new_column_by_commit(graph, col_commit);
      if (j >= 0 && graph->columns[i].is_merge_parent)
        graph->new_columns[j].is_merge_parent = 1;
    }
  }

  graph->commit_in_columns = is_commit_in_columns;

  /*
   * If graph_max_lanes is set, cap the width
   */
  if (graph->revs->graph_max_lanes > 0) {
    /*
     * width of "| " per lanes plus truncation mark "~ ".
     * Allow commits from merges to align to the merged lane.
     */
    int max_width = graph->revs->graph_max_lanes * 2 + 2;
    if (graph->width > max_width)
      graph->width = max_width;
  }

  /*
   * Shrink mapping_size to be the minimum necessary
   */
  while (graph->mapping_size > 1 &&
         graph->mapping[graph->mapping_size - 1] < 0)
    graph->mapping_size--;
}

static int graph_num_dashed_parents(struct git_graph *graph)
{
  return graph->num_parents + graph->merge_layout - 3;
}

static int graph_num_expansion_rows(struct git_graph *graph)
{
  /*
   * Normally, we need two expansion rows for each dashed parent line from
   * an octopus merge:
   *
   *    | *
   *    | |\
   *    | | \
   *    | |  \
   *    | *-. \
   *    | |\ \ \
   *
   * If the merge is skewed to the left, then its parents occupy one less
   * column, and we don't need as many expansion rows to route around it;
   * in some cases that means we don't need any expansion rows at all:
   *
   *    | *
   *    | |\
   *    | * \
   *    |/|\ \
   */
  return graph_num_dashed_parents(graph) * 2;
}

static int graph_needs_pre_commit_line(struct git_graph *graph)
{
  return graph->num_parents >= 3 &&
         graph->commit_index < (graph->num_columns - 1) &&
         graph->expansion_row < graph_num_expansion_rows(graph);
}

struct commit *graph_pop_lookahead(struct git_graph *graph)
{
  struct commit *c;

  if (!graph->lookahead_nr)
    return NULL;

  c = graph->lookahead[0];
  if (!c)
    BUG("lookahead buffer has %d entries but the first one is NULL",
        graph->lookahead_nr);

  graph->lookahead[0] = graph->lookahead[1];
  graph->lookahead[1] = NULL;
  graph->lookahead_nr--;
  return c;
}

int graph_get_lookahead_room(struct git_graph *graph)
{
  return (int)ARRAY_SIZE(graph->lookahead) - graph->lookahead_nr;
}

void graph_push_lookahead(struct git_graph *graph, struct commit *c)
{
  if (!graph_get_lookahead_room(graph))
    BUG("pushing into lookahead buffer when it is already full");

  graph->lookahead[graph->lookahead_nr++] = c;
}

/*
 * A commit can be a visual root when:
 *
 * - It has no parents.
 *
 * - It has parents but they are all filtered out and
 *   commit->parents arrives NULL.
 *
 * - Its parents are uninteresting.
 *
 * - It is not a boundary commit. Boundary commits also have no visible
 *   parents, but they are not selected as visual roots because they cannot
 *   cause the ambiguity of being vertically adjacent because:
 *
 *   1. A boundary only appears because an included commit is its child.
 *      Children are always above, and the renderer draws an edge down to
 *      the boundary from that child. Rather than starting a column like a
 *      visual root would do, it inherits its child column.
 *
 *   2. Included commits cannot appear below a boundary. Boundaries are
 *      ancestors of the exclusion point; if an included commit were an
 *      ancestor of the boundary it would be excluded and not rendered.
 *      Boundaries therefore always sink to the bottom.
 */
static int graph_is_visual_root_candidate(struct commit *c, struct git_graph *graph)
{
  struct commit_list *p;

  if (c->object.flags & BOUNDARY)
    return 0;
  for (p = c->parents; p; p = p->next)
    if (graph_is_interesting(graph, p->item))
      return 0;
  return 1;
}

static int graph_is_visual_root(struct git_graph *graph,
        struct graph_lookahead_flags *flags)
{
  /*
   * This must be only called for the current commit as graph contains
   * the state for the current commit only.
   *
   * To check if a commit is a visual root, call graph_is_visual_root_candidate()
   * but we won't know if it is really a visual root until we get to the
   * next commit state.
   *
   * The current commit is an actual visual root if it is a candidate and
   * the commit is not a non-first parent of a merge.
   *
   *   *
   *   |\
   *   | *    <- it is a visual root candidate but it shouldn't be indented
   *   *         because it is already connected by an edge.
   *   ^         if commit_in_columns && is_merge_parent means the commit
   *   |         was put by a merge and is connected.
   *   |
   *   `-------- if !is_next_visible means we're on the last commit, avoid
   *             indentation unless the one before is a visual root, then
   *             we need to differentiate from the one above.
   *
   * If next_has_columns means that the next commit has
   * already a column, so it will not be rendered below, the
   * current commit has to act as the last commit and omit
   * indentation.
   */
  return graph_is_visual_root_candidate(graph->commit, graph) &&
         !(graph->commit_in_columns &&
     graph->columns[graph->commit_index].is_merge_parent) &&
         flags->is_next_visible &&
         (!flags->next_has_column || graph->visual_root_depth > 0);
}

/*
 * Peeks the next commits via the lookahead buffer and sets the lookahead flags.
 */
static void graph_peek_next_visible(struct git_graph *graph,
            struct graph_lookahead_flags *flags)
{
  flags->is_next_visible = 0;
  flags->is_next_visual_root = 0;
  flags->next_has_column = 0;

  if (!graph->lookahead_nr)
    return;

  flags->is_next_visible = 1;
  flags->next_has_column =
    graph_find_new_column_by_commit(graph, graph->lookahead[0]) >= 0;

  if (!graph_is_visual_root_candidate(graph->lookahead[0], graph))
    return;

  if (graph->lookahead_nr >= 2)
    flags->is_next_visual_root = 1;
}

static int graph_needs_pre_root_line(struct git_graph *graph)
{
  return graph->commit_in_columns && graph->is_visual_root &&
         graph->num_columns > 0 && !graph->visual_root_cascade &&
         !graph->revs->no_graph_indent;
}

void graph_update(struct git_graph *graph, struct commit *commit)
{
  struct commit_list *parent;
  struct graph_lookahead_flags flags;

  /*
   * Set the new commit
   */
  graph->commit = commit;

  /*
   * Count how many interesting parents this commit has
   */
  graph->num_parents = 0;
  for (parent = first_interesting_parent(graph);
       parent;
       parent = next_interesting_parent(graph, parent))
  {
    graph->num_parents++;
  }

  /*
   * Store the old commit_index in prev_commit_index.
   * graph_update_columns() will update graph->commit_index for this
   * commit.
   */
  graph->prev_commit_index = graph->commit_index;

  /*
   * Call graph_update_columns() to update
   * columns, new_columns, and mapping.
   */
  graph_update_columns(graph);

  graph_peek_next_visible(graph, &flags);

  graph->is_visual_root = graph_is_visual_root(graph, &flags);

  if (graph->is_visual_root) {
    /*
     * If next is a visual root we can omit the indent for the first
     * visual root and start cascading.
     */
    if (!graph->visual_root_depth && flags.is_next_visual_root)
      graph->visual_root_cascade = 1;

    /*
     * We wrap the cascading at a max of four columns at most, after
     * that we wrap it back to the initial column.
     *
     * This could cause ambiguity in case of the next commit not
     * being a visual root and be at the initial column after the
     * first wrap.
     *
     * In case of being a non-visual-root the next, stop the
     * cascading to get the commit indented.
     */
    if (!flags.is_next_visual_root &&
        graph->visual_root_depth &&
        !(graph->visual_root_depth % 4))
      graph->visual_root_cascade = 0;

    graph->visual_root_depth++;
  } else {
    graph->visual_root_depth = 0;
    graph->visual_root_cascade = 0;
  }

  graph->expansion_row = 0;

  /*
   * Update graph->state.
   * Note that we don't call graph_update_state() here, since
   * we don't want to update graph->prev_state.  No line for
   * graph->state was ever printed.
   *
   * If the previous commit didn't get to the GRAPH_PADDING state,
   * it never finished its output.  Goto GRAPH_SKIP, to print out
   * a line to indicate that portion of the graph is missing.
   *
   * If there are 3 or more parents, we may need to print extra rows
   * before the commit, to expand the branch lines around it and make
   * room for it.  We need to do this only if there is a branch row
   * (or more) to the right of this commit.
   *
   * If it is a visual root, we need to print an extra row to
   * connect the indentation.
   *
   * If there are less than 3 parents, we can immediately print the
   * commit line.
   */
  if (graph->state != GRAPH_PADDING)
    graph->state = GRAPH_SKIP;
  else if (graph_needs_pre_root_line(graph))
    graph->state = GRAPH_PRE_ROOT;
  else if (graph_needs_pre_commit_line(graph))
    graph->state = GRAPH_PRE_COMMIT;
  else
    graph->state = GRAPH_COMMIT;
}

static int graph_is_mapping_correct(struct git_graph *graph)
{
  int i;

  /*
   * The mapping is up to date if each entry is at its target,
   * or is 1 greater than its target.
   * (If it is 1 greater than the target, '/' will be printed, so it
   * will look correct on the next row.)
   */
  for (i = 0; i < graph->mapping_size; i++) {
    int target = graph->mapping[i];
    if (target < 0)
      continue;
    if (target == (i / 2))
      continue;
    return 0;
  }

  return 1;
}

static void graph_pad_horizontally(struct git_graph *graph, struct graph_line *line)
{
  /*
   * Add additional spaces to the end of the strbuf, so that all
   * lines for a particular commit have the same width.
   *
   * This way, fields printed to the right of the graph will remain
   * aligned for the entire commit.
   */
  if (line->width < graph->width)
    graph_line_addchars(line, ' ', graph->width - line->width);
}

static void graph_output_padding_line(struct git_graph *graph,
              struct graph_line *line)
{
  int i;

  /*
   * Output a padding row, that leaves all branch lines unchanged
   */
  for (i = 0; i < graph->num_new_columns; i++) {
    if (graph_needs_truncation(graph, i)) {
      graph_line_addstr(line, "~ ");
      break;
    }
    graph_line_write_column(line, &graph->new_columns[i], '|');
    graph_line_addch(line, ' ');
  }
}


int graph_width(struct git_graph *graph)
{
  return graph->width;
}


static void graph_output_skip_line(struct git_graph *graph, struct graph_line *line)
{
  /*
   * Output an ellipsis to indicate that a portion
   * of the graph is missing.
   */
  graph_line_addstr(line, "...");

  if (graph_needs_pre_commit_line(graph))
    graph_update_state(graph, GRAPH_PRE_COMMIT);
  else
    graph_update_state(graph, GRAPH_COMMIT);
}

static void graph_output_pre_commit_line(struct git_graph *graph,
           struct graph_line *line)
{
  int i, seen_this;

  /*
   * This function formats a row that increases the space around a commit
   * with multiple parents, to make room for it.  It should only be
   * called when there are 3 or more parents.
   *
   * We need 2 extra rows for every parent over 2.
   */
  assert(graph->num_parents >= 3);

  /*
   * graph->expansion_row tracks the current expansion row we are on.
   * It should be in the range [0, num_expansion_rows - 1]
   */
  assert(0 <= graph->expansion_row &&
         graph->expansion_row < graph_num_expansion_rows(graph));

  /*
   * Output the row
   */
  seen_this = 0;
  for (i = 0; i < graph->num_columns; i++) {
    struct column *col = &graph->columns[i];
    if (col->commit == graph->commit) {
      seen_this = 1;
      graph_line_write_column(line, col, '|');
      graph_line_addchars(line, ' ', graph->expansion_row);
    } else if (seen_this && graph_needs_truncation(graph, i)) {
      graph_line_addstr(line, "~ ");
      break;
    } else if (seen_this && (graph->expansion_row == 0)) {
      /*
       * This is the first line of the pre-commit output.
       * If the previous commit was a merge commit and
       * ended in the GRAPH_POST_MERGE state, all branch
       * lines after graph->prev_commit_index were
       * printed as "\" on the previous line.  Continue
       * to print them as "\" on this line.  Otherwise,
       * print the branch lines as "|".
       */
      if (graph->prev_state == GRAPH_POST_MERGE &&
          graph->prev_commit_index < i)
        graph_line_write_column(line, col, '\\');
      else
        graph_line_write_column(line, col, '|');
    } else if (seen_this && (graph->expansion_row > 0)) {
      graph_line_write_column(line, col, '\\');
    } else {
      graph_line_write_column(line, col, '|');
    }
    graph_line_addch(line, ' ');
  }

  /*
   * Increment graph->expansion_row,
   * and move to state GRAPH_COMMIT if necessary
   */
  graph->expansion_row++;
  if (!graph_needs_pre_commit_line(graph))
    graph_update_state(graph, GRAPH_COMMIT);
}

static void graph_output_commit_char(struct git_graph *graph, struct graph_line *line)
{
  /*
   * For boundary commits, print 'o'
   * (We should only see boundary commits when revs->boundary is set.)
   */
  if (graph->commit->object.flags & BOUNDARY) {
    assert(graph->revs->boundary);
    graph_line_addch(line, 'o');
    return;
  }

  /*
   * get_revision_mark() handles all other cases without assert()
   */
  graph_line_addstr(line, get_revision_mark(graph->revs, graph->commit));
}

/*
 * Draw the horizontal dashes of an octopus merge.
 */
static void graph_draw_octopus_merge(struct git_graph *graph, struct graph_line *line)
{
  /*
   * The parents of a merge commit can be arbitrarily reordered as they
   * are mapped onto display columns, for example this is a valid merge:
   *
   *  | | *---.
   *  | | |\ \ \
   *  | | |/ / /
   *  | |/| | /
   *  | |_|_|/
   *  |/| | |
   *  3 1 0 2
   *
   * The numbers denote which parent of the merge each visual column
   * corresponds to; we can't assume that the parents will initially
   * display in the order given by new_columns.
   *
   * To find the right color for each dash, we need to consult the
   * mapping array, starting from the column 2 places to the right of the
   * merge commit, and use that to find out which logical column each
   * edge will collapse to.
   *
   * Commits are rendered once all edges have collapsed to their correct
   * logcial column, so commit_index gives us the right visual offset for
   * the merge commit.
   */

  int i, j;
  struct column *col;

  int dashed_parents = graph_num_dashed_parents(graph);

  for (i = 0; i < dashed_parents; i++) {
    j = graph->mapping[(graph->commit_index + i + 2) * 2];
    col = &graph->new_columns[j];

    graph_line_write_column(line, col, '-');

    /*
     * Commit is at commit_index, each iteration move one lane to
     * the right from the commit.
     */
    if (graph_needs_truncation(graph, graph->commit_index + 1 + i)) {
      graph_line_addstr(line, "~ ");
      break;
    }

    graph_line_write_column(line, col, (i == dashed_parents - 1) ? '.' : '-');
  }

  return;
}

static void graph_output_commit_line(struct git_graph *graph, struct graph_line *line)
{
  int seen_this = 0;
  int i;

  /*
   * Output the row containing this commit
   * Iterate up to and including graph->num_columns,
   * since the current commit may not be in any of the existing
   * columns.  (This happens when the current commit doesn't have any
   * children that we have already processed.)
   */
  seen_this = 0;
  for (i = 0; i <= graph->num_columns; i++) {
    struct column *col = &graph->columns[i];
    struct commit *col_commit;
    if (i == graph->num_columns) {
      if (seen_this)
        break;
      col_commit = graph->commit;
    } else {
      col_commit = graph->columns[i].commit;
    }

    if (col_commit == graph->commit) {
      seen_this = 1;
      if (graph->is_visual_root && !graph->revs->no_graph_indent) {
        int depth = graph->visual_root_depth;
        /*
         * Each visual column is 2 characters wide.
         * Omit the indentation for the first visual
         * root in cascade mode.
         *
         * Have a max of 4 columns when cascading, after
         * that wrap it and repeat.
         */
        int padding = ((depth - graph->visual_root_cascade) % 4) * 2;
        graph_line_addchars(line, ' ', padding);
        graph->width += padding;
      }
      graph_output_commit_char(graph, line);

      if (graph_needs_truncation(graph, i)) {
        graph_line_addch(line, ' ');
        break;
      }

      if (graph->num_parents > 2)
        graph_draw_octopus_merge(graph, line);
    } else if (graph_needs_truncation(graph, i)) {
      graph_line_addstr(line, "~ ");
      seen_this = 1;
      break;
    } else if (seen_this && (graph->edges_added > 1)) {
      graph_line_write_column(line, col, '\\');
    } else if (seen_this && (graph->edges_added == 1)) {
      /*
       * This is either a right-skewed 2-way merge
       * commit, or a left-skewed 3-way merge.
       * There is no GRAPH_PRE_COMMIT stage for such
       * merges, so this is the first line of output
       * for this commit.  Check to see what the previous
       * line of output was.
       *
       * If it was GRAPH_POST_MERGE, the branch line
       * coming into this commit may have been '\',
       * and not '|' or '/'.  If so, output the branch
       * line as '\' on this line, instead of '|'.  This
       * makes the output look nicer.
       */
      if (graph->prev_state == GRAPH_POST_MERGE &&
          graph->prev_edges_added > 0 &&
          graph->prev_commit_index < i)
        graph_line_write_column(line, col, '\\');
      else
        graph_line_write_column(line, col, '|');
    } else if (graph->prev_state == GRAPH_COLLAPSING &&
         graph->old_mapping[2 * i + 1] == i &&
         graph->mapping[2 * i] < i) {
      graph_line_write_column(line, col, '/');
    } else {
      graph_line_write_column(line, col, '|');
    }
    graph_line_addch(line, ' ');
  }

  /*
   * Update graph->state
   *
   * If the commit is a merge and the first parent is in a visible lane,
   * then the GRAPH_POST_MERGE is needed to draw the merge lane.
   *
   * If the commit is over the truncation limit, but the first parent is on
   * a visible lane, then we still need the merge lane but truncated.
   *
   * If both commit and first parent are over the truncation limit, then
   * there's no need to draw the merge lane because it would work as a
   * padding lane.
   */
  if (graph->num_parents > 1) {
    if (!graph_needs_truncation(graph, graph->commit_index)) {
      graph_update_state(graph, GRAPH_POST_MERGE);
    } else {
      struct commit_list *p = first_interesting_parent(graph);
      int lane;

      /*
       * graph->num_parents are found using first_interesting_parent
       * and next_interesting_parent so it can't be a scenario
       * where num_parents > 1 and there are no interesting parents
       */
      if (!p)
        BUG("num_parents > 1 but no interesting parent");

      lane = graph_find_new_column_by_commit(graph, p->item);

      if (!graph_needs_truncation(graph, lane))
        graph_update_state(graph, GRAPH_POST_MERGE);
      else if (graph_is_mapping_correct(graph))
        graph_update_state(graph, GRAPH_PADDING);
      else
        graph_update_state(graph, GRAPH_COLLAPSING);
    }
  } else if (graph_is_mapping_correct(graph)) {
    graph_update_state(graph, GRAPH_PADDING);
  } else {
    graph_update_state(graph, GRAPH_COLLAPSING);
  }
}

static const char merge_chars[] = {'/', '|', '\\'};

static void graph_output_post_merge_line(struct git_graph *graph, struct graph_line *line)
{
  int seen_this = 0;
  int i, j;

  struct commit_list *first_parent = first_interesting_parent(graph);
  struct column *parent_col = NULL;

  /*
   * Output the post-merge row
   */
  for (i = 0; i <= graph->num_columns; i++) {
    struct column *col = &graph->columns[i];
    struct commit *col_commit;
    if (i == graph->num_columns) {
      if (seen_this)
        break;
      col_commit = graph->commit;
    } else {
      col_commit = col->commit;
    }

    if (col_commit == graph->commit) {
      /*
       * Since the current commit is a merge find
       * the columns for the parent commits in
       * new_columns and use those to format the
       * edges.
       */
      struct commit_list *parents = first_parent;
      int par_column;
      int idx = graph->merge_layout;
      char c;
      int truncated = 0;
      seen_this = 1;

      for (j = 0; j < graph->num_parents; j++) {
        par_column = graph_find_new_column_by_commit(graph, parents->item);
        assert(par_column >= 0);

        c = merge_chars[idx];
        graph_line_write_column(line, &graph->new_columns[par_column], c);

        /*
         * j counts parents, it needs to be halved to be
         * comparable with i. Don't truncate if there are
         * no more lanes to print (end of the lane)
         */
        if (graph_needs_truncation(graph, j / 2 + i) &&
            j / 2 + i <= graph->num_columns) {
          if ((j + i * 2) % 2 != 0)
            graph_line_addch(line, ' ');
          graph_line_addstr(line, "~ ");
          truncated = 1;
          break;
        }

        if (idx == 2) {
          /*
           * Check if the next lane needs truncation
           * to avoid having the padding doubled
           */
          if (graph_needs_truncation(graph, (j + 1) / 2 + i) &&
              j < graph->num_parents - 1) {
            graph_line_addstr(line, "~ ");
            truncated = 1;
            break;
          } else if (graph->edges_added > 0 || j < graph->num_parents - 1)
            graph_line_addch(line, ' ');
        } else {
          idx++;
        }
        parents = next_interesting_parent(graph, parents);
      }
      if (truncated)
        break;
      if (graph->edges_added == 0)
        graph_line_addch(line, ' ');
    } else if (graph_needs_truncation(graph, i)) {
      graph_line_addstr(line, "~ ");
      break;
    } else if (seen_this) {
      if (graph->edges_added > 0)
        graph_line_write_column(line, col, '\\');
      else
        graph_line_write_column(line, col, '|');
      /*
       * If it's between two lanes and next would be truncated,
       * don't add space padding.
       */
      if (!graph_needs_truncation(graph, i + 1))
        graph_line_addch(line, ' ');
    } else {
      graph_line_write_column(line, col, '|');
      if (graph->merge_layout != 0 || i != graph->commit_index - 1) {
        if (parent_col)
          graph_line_write_column(
            line, parent_col, '_');
        else
          graph_line_addch(line, ' ');
      }
    }

    if (col_commit == first_parent->item)
      parent_col = col;
  }

  /*
   * Update graph->state
   */
  if (graph_is_mapping_correct(graph))
    graph_update_state(graph, GRAPH_PADDING);
  else
    graph_update_state(graph, GRAPH_COLLAPSING);
}

static void graph_output_collapsing_line(struct git_graph *graph, struct graph_line *line)
{
  int i;
  short used_horizontal = 0;
  int horizontal_edge = -1;
  int horizontal_edge_target = -1;
  int truncated = 0;

  /*
   * Swap the mapping and old_mapping arrays
   */
  SWAP(graph->mapping, graph->old_mapping);

  /*
   * Clear out the mapping array
   */
  for (i = 0; i < graph->mapping_size; i++)
    graph->mapping[i] = -1;

  for (i = 0; i < graph->mapping_size; i++) {
    int target = graph->old_mapping[i];
    if (target < 0)
      continue;

    /*
     * Since update_columns() always inserts the leftmost
     * column first, each branch's target location should
     * always be either its current location or to the left of
     * its current location.
     *
     * We never have to move branches to the right.  This makes
     * the graph much more legible, since whenever branches
     * cross, only one is moving directions.
     */
    assert(target * 2 <= i);

    if (target * 2 == i) {
      /*
       * This column is already in the
       * correct place
       */
      assert(graph->mapping[i] == -1);
      graph->mapping[i] = target;
    } else if (graph->mapping[i - 1] < 0) {
      /*
       * Nothing is to the left.
       * Move to the left by one
       */
      graph->mapping[i - 1] = target;
      /*
       * If there isn't already an edge moving horizontally
       * select this one.
       */
      if (horizontal_edge == -1) {
        int j;
        horizontal_edge = i;
        horizontal_edge_target = target;
        /*
         * The variable target is the index of the graph
         * column, and therefore target*2+3 is the
         * actual screen column of the first horizontal
         * line.
         */
        for (j = (target * 2)+3; j < (i - 2); j += 2)
          graph->mapping[j] = target;
      }
    } else if (graph->mapping[i - 1] == target) {
      /*
       * There is a branch line to our left
       * already, and it is our target.  We
       * combine with this line, since we share
       * the same parent commit.
       *
       * We don't have to add anything to the
       * output or mapping, since the
       * existing branch line has already taken
       * care of it.
       */
    } else {
      /*
       * There is a branch line to our left,
       * but it isn't our target.  We need to
       * cross over it.
       *
       * The space just to the left of this
       * branch should always be empty.
       */
      assert(graph->mapping[i - 1] > target);
      assert(graph->mapping[i - 2] < 0);
      graph->mapping[i - 2] = target;
      /*
       * Mark this branch as the horizontal edge to
       * prevent any other edges from moving
       * horizontally.
       */
      if (horizontal_edge == -1) {
        int j;
        horizontal_edge_target = target;
        horizontal_edge = i - 1;

        for (j = (target * 2) + 3; j < (i - 2); j += 2)
          graph->mapping[j] = target;
      }
    }
  }

  /*
   * Copy the current mapping array into old_mapping
   */
  COPY_ARRAY(graph->old_mapping, graph->mapping, graph->mapping_size);

  /*
   * The new mapping may be 1 smaller than the old mapping
   */
  if (graph->mapping[graph->mapping_size - 1] < 0)
    graph->mapping_size--;

  /*
   * Output out a line based on the new mapping info
   */
  for (i = 0; i < graph->mapping_size; i++) {
    int target = graph->mapping[i];

    if (!truncated && graph_needs_truncation(graph, i / 2)) {
      graph_line_addstr(line, "~ ");
      truncated = 1;
    }

    if (target < 0) {
      if (!truncated)
        graph_line_addch(line, ' ');
    } else if (target * 2 == i) {
      if (!truncated)
        graph_line_write_column(line, &graph->new_columns[target], '|');
    } else if (target == horizontal_edge_target &&
         i != horizontal_edge - 1) {
      /*
       * Set the mappings for all but the
       * first segment to -1 so that they
       * won't continue into the next line.
       */
      if (i != (target * 2)+3)
        graph->mapping[i] = -1;
      used_horizontal = 1;
      if (!truncated)
        graph_line_write_column(line, &graph->new_columns[target], '_');
    } else {
      if (used_horizontal && i < horizontal_edge)
        graph->mapping[i] = -1;
      if (!truncated)
        graph_line_write_column(line, &graph->new_columns[target], '/');
    }
  }

  /*
   * If graph->mapping indicates that all of the branch lines
   * are already in the correct positions, we are done.
   * Otherwise, we need to collapse some branch lines together.
   */
  if (graph_is_mapping_correct(graph))
    graph_update_state(graph, GRAPH_PADDING);
}

static void graph_output_pre_root_line(struct git_graph *graph, struct graph_line *line)
{
  /*
   * This function adds a row before a visual root, to connect the
   * branch to the indented commit. It must only be called on a
   * visual root.
   */
  if (!graph->is_visual_root)
    BUG("commit must be a visual root to call pre_root_line");

  for (int i = 0; i < graph->num_columns; i++) {
    struct column *col = &graph->columns[i];
    if (col->commit == graph->commit) {
      graph_line_addch(line, ' ');
      graph_line_write_column(line, col, '\\');
    } else {
      graph_line_write_column(line, col, '|');
    }
    graph_line_addch(line, ' ');
  }

  graph_update_state(graph, GRAPH_COMMIT);
}

int graph_next_line(struct git_graph *graph, struct strbuf *sb)
{
  int shown_commit_line = 0;
  struct graph_line line = { .buf = sb, .width = 0 };

  /*
   * We could conceivable be called with a NULL commit
   * if our caller has a bug, and invokes graph_next_line()
   * immediately after graph_init(), without first calling
   * graph_update().  Return without outputting anything in this
   * case.
   */
  if (!graph->commit)
    return -1;

  switch (graph->state) {
  case GRAPH_PADDING:
    graph_output_padding_line(graph, &line);
    break;
  case GRAPH_SKIP:
    graph_output_skip_line(graph, &line);
    break;
  case GRAPH_PRE_COMMIT:
    graph_output_pre_commit_line(graph, &line);
    break;
  case GRAPH_PRE_ROOT:
    graph_output_pre_root_line(graph, &line);
    break;
  case GRAPH_COMMIT:
    graph_output_commit_line(graph, &line);
    shown_commit_line = 1;
    break;
  case GRAPH_POST_MERGE:
    graph_output_post_merge_line(graph, &line);
    break;
  case GRAPH_COLLAPSING:
    graph_output_collapsing_line(graph, &line);
    break;
  }

  graph_pad_horizontally(graph, &line);
  return shown_commit_line;
}

static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
{
  int i;
  struct graph_line line = { .buf = sb, .width = 0 };

  if (graph->state != GRAPH_COMMIT) {
    graph_next_line(graph, sb);
    return;
  }

  /*
   * Output the row containing this commit
   * Iterate up to and including graph->num_columns,
   * since the current commit may not be in any of the existing
   * columns.  (This happens when the current commit doesn't have any
   * children that we have already processed.)
   */
  for (i = 0; i < graph->num_columns; i++) {
    struct column *col = &graph->columns[i];

    if (graph_needs_truncation(graph, i)) {
      graph_line_addstr(&line, "~ ");
      break;
    }

    graph_line_write_column(&line, col, '|');

    if (col->commit == graph->commit && graph->num_parents > 2) {
      int len = (graph->num_parents - 2) * 2;
      graph_line_addchars(&line, ' ', len);
    } else {
      graph_line_addch(&line, ' ');
    }
  }

  graph_pad_horizontally(graph, &line);

  /*
   * Update graph->prev_state since we have output a padding line
   */
  graph->prev_state = GRAPH_PADDING;
}

int graph_is_commit_finished(struct git_graph const *graph)
{
  return (graph->state == GRAPH_PADDING);
}

void graph_show_commit(struct git_graph *graph)
{
  struct strbuf msgbuf = STRBUF_INIT;
  int shown_commit_line = 0;

  graph_show_line_prefix(default_diffopt);

  if (!graph)
    return;

  /*
   * When showing a diff of a merge against each of its parents, we
   * are called once for each parent without graph_update having been
   * called.  In this case, simply output a single padding line.
   */
  if (graph_is_commit_finished(graph)) {
    graph_show_padding(graph);
    shown_commit_line = 1;
  }

  while (!shown_commit_line && !graph_is_commit_finished(graph)) {
    shown_commit_line = graph_next_line(graph, &msgbuf);
    fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
      graph->revs->diffopt.file);
    if (!shown_commit_line) {
      putc('\n', graph->revs->diffopt.file);
      graph_show_line_prefix(&graph->revs->diffopt);
    }
    strbuf_setlen(&msgbuf, 0);
  }

  strbuf_release(&msgbuf);
}

void graph_show_oneline(struct git_graph *graph)
{
  struct strbuf msgbuf = STRBUF_INIT;

  graph_show_line_prefix(default_diffopt);

  if (!graph)
    return;

  graph_next_line(graph, &msgbuf);
  fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
  strbuf_release(&msgbuf);
}

void graph_show_padding(struct git_graph *graph)
{
  struct strbuf msgbuf = STRBUF_INIT;

  graph_show_line_prefix(default_diffopt);

  if (!graph)
    return;

  graph_padding_line(graph, &msgbuf);
  fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
  strbuf_release(&msgbuf);
}

int graph_show_remainder(struct git_graph *graph)
{
  struct strbuf msgbuf = STRBUF_INIT;
  int shown = 0;

  graph_show_line_prefix(default_diffopt);

  if (!graph)
    return 0;

  if (graph_is_commit_finished(graph))
    return 0;

  for (;;) {
    graph_next_line(graph, &msgbuf);
    fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
      graph->revs->diffopt.file);
    strbuf_setlen(&msgbuf, 0);
    shown = 1;

    if (!graph_is_commit_finished(graph)) {
      putc('\n', graph->revs->diffopt.file);
      graph_show_line_prefix(&graph->revs->diffopt);
    } else {
      break;
    }
  }
  strbuf_release(&msgbuf);

  return shown;
}

static void graph_show_strbuf(struct git_graph *graph,
            FILE *file,
            struct strbuf const *sb)
{
  char *p;

  /*
   * Print the strbuf line by line,
   * and display the graph info before each line but the first.
   */
  p = sb->buf;
  while (p) {
    size_t len;
    char *next_p = strchr(p, '\n');
    if (next_p) {
      next_p++;
      len = next_p - p;
    } else {
      len = (sb->buf + sb->len) - p;
    }
    fwrite(p, sizeof(char), len, file);
    if (next_p && *next_p != '\0')
      graph_show_oneline(graph);
    p = next_p;
  }
}

void graph_show_commit_msg(struct git_graph *graph,
         FILE *file,
         struct strbuf const *sb)
{
  int newline_terminated;

  /*
   * Show the commit message
   */
  graph_show_strbuf(graph, file, sb);

  if (!graph)
    return;

  newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');

  /*
   * If there is more output needed for this commit, show it now
   */
  if (!graph_is_commit_finished(graph)) {
    /*
     * If sb doesn't have a terminating newline, print one now,
     * so we can start the remainder of the graph output on a
     * new line.
     */
    if (!newline_terminated)
      putc('\n', file);

    graph_show_remainder(graph);

    /*
     * If sb ends with a newline, our output should too.
     */
    if (newline_terminated)
      putc('\n', file);
  }
}

Coverage Report

Created: 2026-10-17 07:15