[PATCH 1/4] Add history graph API

@@ -0,0 +1,108 @@
+history graph API
+=================
+
+The graph API is used to draw a text-based representation of the commit
+history.  The API generates the graph in a line-by-line fashion.
+
+Calling sequence
+----------------
+
+* Create a `struct git_graph` by calling `graph_init()`
+
+* Use the revision walking API to walk through a group of contiguous commits.
+
+* For each commit you walk through, call `graph_update()`.  Then call
+  `graph_next_line()` repeatedly, until `graph_is_commit_finished()` returns
+  non-zero.  Each call go `graph_next_line()` will output a single line of the
+  graph.  The resulting lines will not contain any newlines.
+  `graph_next_line()` returns 1 if the resulting line contains the current
+  commit, or 0 if this is merely a line needed to adjust the graph before or
+  after the current commit.  This return value can be used to determine where
+  to print the commit summary information alongside the graph output.
+
+Data structure
+--------------
+`struct git_graph` is an opaque data type used to store the current graph
+state.
+
+Limitations
+-----------
+
+* `graph_update()` must be called with commits in topological order.  The
+  commits must also be a contiguous group--intervening parents should not
+  be ommitted.  Otherwise, the graph API cannot determine the proper
+  parent-child relationships between the commits.  If intervening parents
+  are ommitted, the next ancestor that is used will appear to be on a
+  separate branch in the graph.
+
+* The graph API does not currently support reverse commit ordering.  In
+  order to implement reverse ordering, the graphing API needs an
+  (efficient) mechanism to find the children of a commit.
+
+Sample usage
+------------
+
+------------
+struct commit *commit;
+struct git_graph *graph = graph_init();
+
+while ((commit = get_revision(opts)) != NULL) {
+	graph_update(graph, commit);
+	while (!graph_is_commit_finished(graph))
+	{
+		struct strbuf sb;
+		int is_commit_line;
+
+		strbuf_init(&sb, 0);
+		is_commit_line = graph_next_line(graph, &sb);
+		fputs(sb.buf, stdout);
+
+		if (is_commit_line)
+			log_tree_commit(opts, commit);
+		else
+			putchar(opts->diffopt.line_termination);
+	}
+}
+
+graph_release(graph);
+------------
+
+Sample output
+-------------
+
+The following is an example of the output from the graph API.  This output does
+not include any commit summary information--callers of responsible for
+outputting that information, if desired.
+
+------------
+*
+*
+M
+|\
+* |
+| | *
+| \ \
+|  \ \
+M-. \ \
+|\ \ \ \
+| | * | |
+| | | | | *
+| | | | | *
+| | | | | M
+| | | | | |\
+| | | | | | *
+| * | | | | |
+| | | | | M  \
+| | | | | |\  |
+| | | | * | | |
+| | | | * | | |
+* | | | | | | |
+| |/ / / / / /
+|/| / / / / /
+* | | | | | |
+|/ / / / / /
+* | | | | |
+| | | | | *
+| | | | |/
+| | | | *
+------------

@@ -345,6 +345,7 @@ LIB_H += diff.h
 LIB_H += dir.h
 LIB_H += fsck.h
 LIB_H += git-compat-util.h
+LIB_H += graph.h
 LIB_H += grep.h
 LIB_H += hash.h
 LIB_H += list-objects.h

@@ -409,6 +410,7 @@ LIB_OBJS += entry.o
 LIB_OBJS += environment.o
 LIB_OBJS += exec_cmd.o
 LIB_OBJS += fsck.o
+LIB_OBJS += graph.o
 LIB_OBJS += grep.o
 LIB_OBJS += hash.o
 LIB_OBJS += help.o

@@ -0,0 +1,711 @@
+#include "cache.h"
+#include "commit.h"
+#include "graph.h"
+
+/*
+ * TODO:
+ * - Add colors to the graph.
+ *   Pick a color for each column, and print all characters
+ *   in that column with the specified color.
+ *
+ * - 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.
+ *
+ * - The output during the GRAPH_PRE_COMMIT and GRAPH_COLLAPSING states
+ *   could be made more compact by printing horizontal lines, instead of
+ *   long diagonal lines.  For example, during collapsing, something like
+ *   this:          instead of this:
+ *   | | | | |      | | | | |
+ *   | |_|_|/       | | | |/
+ *   |/| | |        | | |/|
+ *   | | | |        | |/| |
+ *                  |/| | |
+ *                  | | | |
+ *
+ *   If there are several parallel diagonal lines, they will need to be
+ *   replaced with horizontal lines on subsequent rows.
+ */
+
+struct column {
+	/*
+	 * The parent commit of this column.
+	 */
+	struct commit *commit;
+	/*
+	 * XXX: Once we add support for colors, struct column could also
+	 * contain the color of its branch line.
+	 */
+};
+
+enum graph_state {
+	GRAPH_PADDING,
+	GRAPH_SKIP,
+	GRAPH_PRE_COMMIT,
+	GRAPH_COMMIT,
+	GRAPH_POST_MERGE,
+	GRAPH_COLLAPSING
+};
+
+struct git_graph {
+	/*
+	 * The commit currently being processed
+	 */
+	struct commit *commit;
+	/*
+	 * The number of parents this commit has.
+	 * (Stored so we don't have to walk over them each time we need
+	 * this number)
+	 */
+	int num_parents;
+	/*
+	 * 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 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 new_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 temporary array for computing the next mapping state
+	 * while we are outputting a mapping line.  This is stored as part
+	 * of the git_graph simply so we don't have to allocate a new
+	 * temporary array each time we have to output a collapsing line.
+	 */
+	int *new_mapping;
+};
+
+struct git_graph *graph_init()
+{
+	struct git_graph *graph = xmalloc(sizeof(struct git_graph));
+	graph->commit = NULL;
+	graph->num_parents = 0;
+	graph->expansion_row = 0;
+	graph->state = GRAPH_PADDING;
+	graph->num_columns = 0;
+	graph->num_new_columns = 0;
+	graph->mapping_size = 0;
+
+	/*
+	 * Allocate a reasonably large default number of columns
+	 * We'll automatically grow columns later if we need more room.
+	 */
+	graph->column_capacity = 30;
+	graph->columns = xmalloc(sizeof(struct column) *
+				 graph->column_capacity);
+	graph->new_columns = xmalloc(sizeof(struct column) *
+				     graph->column_capacity);
+	graph->mapping = xmalloc(sizeof(int) * 2 * graph->column_capacity);
+	graph->new_mapping = xmalloc(sizeof(int) * 2 * graph->column_capacity);
+
+	return graph;
+}
+
+void graph_release(struct git_graph *graph)
+{
+	free(graph->columns);
+	free(graph->new_columns);
+	free(graph->mapping);
+	free(graph);
+}
+
+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);
+
+	graph->columns = xrealloc(graph->columns,
+				  sizeof(struct column) *
+				  graph->column_capacity);
+	graph->new_columns = xrealloc(graph->new_columns,
+				      sizeof(struct column) *
+				      graph->column_capacity);
+	graph->mapping = xrealloc(graph->mapping,
+				  sizeof(int) * 2 * graph->column_capacity);
+	graph->new_mapping = xrealloc(graph->new_mapping,
+				      sizeof(int) * 2 * graph->column_capacity);
+}
+
+static void graph_insert_into_new_columns(struct git_graph *graph,
+					  struct commit *commit,
+					  int mapping_index)
+{
+	int i;
+
+	/*
+	 * If the commit is already in the new_columns list, we don't need to
+	 * add it.  Just update the mapping correctly.
+	 */
+	for (i = 0; i < graph->num_new_columns; ++i) {
+		if (graph->new_columns[i].commit == commit) {
+			graph->mapping[mapping_index] = i;
+			return;
+		}
+	}
+
+	/*
+	 * This commit isn't already in new_columns.  Add it.
+	 */
+	graph->new_columns[graph->num_new_columns].commit = commit;
+	graph->mapping[mapping_index] = graph->num_new_columns;
+	++graph->num_new_columns;
+}
+
+static void graph_update_columns(struct git_graph *graph)
+{
+	struct commit_list *parent;
+	struct column *tmp_columns;
+	int max_new_columns;
+	int mapping_idx;
+	int i, seen_this;
+
+	/*
+	 * 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.
+	 */
+	tmp_columns = graph->columns;
+	graph->columns = graph->new_columns;
+	graph->num_columns = graph->num_new_columns;
+
+	graph->new_columns = tmp_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;
+
+	/*
+	 * 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;
+	mapping_idx = 0;
+	for (i = 0; i <= graph->num_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;
+			for (parent = graph->commit->parents;
+			     parent;
+			     parent = parent->next) {
+				graph_insert_into_new_columns(graph,
+							      parent->item,
+							      mapping_idx);
+				mapping_idx += 2;
+			}
+		} else {
+			graph_insert_into_new_columns(graph, col_commit,
+						      mapping_idx);
+			mapping_idx += 2;
+		}
+	}
+
+	/*
+	 * Shrink mapping_size to be the minimum necessary
+	 */
+	while (graph->mapping_size > 1 &&
+	       graph->mapping[graph->mapping_size - 1] < 0)
+		--graph->mapping_size;
+}
+
+void graph_update(struct git_graph *graph, struct commit *commit)
+{
+	struct commit_list *parent;
+
+	/*
+	 * Set the new commit
+	 */
+	graph->commit = commit;
+
+	/*
+	 * Count how many parents this commit has
+	 */
+	graph->num_parents = 0;
+	for (parent = commit->parents; parent; parent = parent->next)
+		++(graph->num_parents);
+
+	/*
+	 * Call graph_update_columns() to update
+	 * columns, new_columns, and mapping.
+	 */
+	graph_update_columns(graph);
+
+	graph->expansion_row = 0;
+
+	/*
+	 * Update graph->state.
+	 *
+	 * 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.
+	 *
+	 * Otherwise, if there are 3 or more parents, we need to print
+	 * extra rows before the commit, to expand the branch lines around
+	 * it and make room for it.
+	 *
+	 * 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->num_parents >= 3)
+		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 strbuf *sb)
+{
+	/*
+	 * 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.
+	 *
+	 * This computation results in 3 extra space to the right in most
+	 * cases, but only 1 extra space if the commit doesn't have any
+	 * children that have already been displayed in the graph (i.e.,
+	 * if the current commit isn't in graph->columns).
+	 */
+	size_t extra;
+	size_t final_width = graph->num_columns + graph->num_parents;
+	if (graph->num_parents < 1)
+		++final_width;
+	final_width *= 2;
+
+	if (sb->len >= final_width)
+		return;
+
+	extra = final_width - sb->len;
+	strbuf_addf(sb, "%*s", extra, "");
+}
+
+static void graph_output_padding_line(struct git_graph *graph,
+				      struct strbuf *sb)
+{
+	int i;
+
+	/*
+	 * 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;
+
+	/*
+	 * Output a padding row, that leaves all branch lines unchanged
+	 */
+	for (i = 0; i < graph->num_new_columns; ++i) {
+		strbuf_addstr(sb, "| ");
+	}
+
+	graph_pad_horizontally(graph, sb);
+}
+
+static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
+{
+	/*
+	 * Output an ellipsis to indicate that a portion
+	 * of the graph is missing.
+	 */
+	strbuf_addstr(sb, "...");
+	graph_pad_horizontally(graph, sb);
+
+	if (graph->num_parents >= 3)
+		graph->state = GRAPH_PRE_COMMIT;
+	else
+		graph->state = GRAPH_COMMIT;
+}
+
+static void graph_output_pre_commit_line(struct git_graph *graph,
+					 struct strbuf *sb)
+{
+	int num_expansion_rows;
+	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);
+	num_expansion_rows = (graph->num_parents - 2) * 2;
+
+	/*
+	 * 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 < num_expansion_rows);
+
+	/*
+	 * 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;
+			strbuf_addf(sb, "| %*s", graph->expansion_row, "");
+		} else if (seen_this) {
+			strbuf_addstr(sb, "\\ ");
+		} else {
+			strbuf_addstr(sb, "| ");
+		}
+	}
+
+	graph_pad_horizontally(graph, sb);
+
+	/*
+	 * Increment graph->expansion_row,
+	 * and move to state GRAPH_COMMIT if necessary
+	 */
+	++graph->expansion_row;
+	if (graph->expansion_row >= num_expansion_rows)
+		graph->state = GRAPH_COMMIT;
+}
+
+void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
+{
+	int seen_this = 0;
+	int i, j;
+
+	/*
+	 * 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 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->num_parents > 1)
+				strbuf_addch(sb, 'M');
+			else
+				strbuf_addch(sb, '*');
+
+			if (graph->num_parents < 2)
+				strbuf_addch(sb, ' ');
+			else if (graph->num_parents == 2)
+				strbuf_addstr(sb, "  ");
+			else {
+				int num_dashes =
+					((graph->num_parents - 2) * 2) - 1;
+				for (j = 0; j < num_dashes; ++j)
+					strbuf_addch(sb, '-');
+				strbuf_addstr(sb, ". ");
+			}
+		} else if (seen_this && (graph->num_parents > 1)) {
+			strbuf_addstr(sb, "\\ ");
+		} else {
+			strbuf_addstr(sb, "| ");
+		}
+	}
+
+	graph_pad_horizontally(graph, sb);
+
+	/*
+	 * Update graph->state
+	 */
+	if (graph->num_parents > 1)
+		graph->state = GRAPH_POST_MERGE;
+	else if (graph_is_mapping_correct(graph))
+		graph->state = GRAPH_PADDING;
+	else
+		graph->state = GRAPH_COLLAPSING;
+}
+
+void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
+{
+	int seen_this = 0;
+	int i, j;
+
+	/*
+	 * Output the post-merge row
+	 */
+	for (i = 0; i <= graph->num_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;
+			strbuf_addch(sb, '|');
+			for (j = 0; j < graph->num_parents - 1; ++j)
+				strbuf_addstr(sb, "\\ ");
+			if (graph->num_parents == 2)
+				strbuf_addch(sb, ' ');
+		} else if (seen_this && (graph->num_parents > 2)) {
+			strbuf_addstr(sb, "\\ ");
+		} else {
+			strbuf_addstr(sb, "| ");
+		}
+	}
+
+	graph_pad_horizontally(graph, sb);
+
+	/*
+	 * Update graph->state
+	 */
+	if (graph_is_mapping_correct(graph))
+		graph->state = GRAPH_PADDING;
+	else
+		graph->state = GRAPH_COLLAPSING;
+}
+
+void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
+{
+	int i;
+	int *tmp_mapping;
+
+	/*
+	 * Clear out the new_mapping array
+	 */
+	for (i = 0; i < graph->mapping_size; ++i)
+		graph->new_mapping[i] = -1;
+
+	for (i = 0; i < graph->mapping_size; ++i) {
+		int target = graph->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->new_mapping[i] == -1);
+			graph->new_mapping[i] = target;
+		} else if (graph->new_mapping[i - 1] < 0) {
+			/*
+			 * Nothing is to the left.
+			 * Move to the left by one
+			 */
+			graph->new_mapping[i - 1] = target;
+		} else if (graph->new_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 new_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->new_mapping[i - 1] > target);
+			assert(graph->new_mapping[i - 2] < 0);
+			graph->new_mapping[i - 2] = target;
+		}
+	}
+
+	/*
+	 * The new mapping may be 1 smaller than the old mapping
+	 */
+	if (graph->new_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->new_mapping[i];
+		if (target < 0)
+			strbuf_addch(sb, ' ');
+		else if (target * 2 == i)
+			strbuf_addch(sb, '|');
+		else
+			strbuf_addch(sb, '/');
+	}
+
+	graph_pad_horizontally(graph, sb);
+
+	/*
+	 * Swap mapping and new_mapping
+	 */
+	tmp_mapping = graph->mapping;
+	graph->mapping = graph->new_mapping;
+	graph->new_mapping = tmp_mapping;
+
+	/*
+	 * 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->state = GRAPH_PADDING;
+}
+
+int graph_next_line(struct git_graph *graph, struct strbuf *sb)
+{
+	switch (graph->state) {
+	case GRAPH_PADDING:
+		graph_output_padding_line(graph, sb);
+		return 0;
+	case GRAPH_SKIP:
+		graph_output_skip_line(graph, sb);
+		return 0;
+	case GRAPH_PRE_COMMIT:
+		graph_output_pre_commit_line(graph, sb);
+		return 0;
+	case GRAPH_COMMIT:
+		graph_output_commit_line(graph, sb);
+		return 1;
+	case GRAPH_POST_MERGE:
+		graph_output_post_merge_line(graph, sb);
+		return 0;
+	case GRAPH_COLLAPSING:
+		graph_output_collapsing_line(graph, sb);
+		return 0;
+	}
+
+	assert(0);
+	return 0;
+}
+
+int graph_is_commit_finished(struct git_graph const *graph)
+{
+	return (graph->state == GRAPH_PADDING);
+}