This new API allows the commit history to be displayed as a text-based
graphical representation.
Signed-off-by: Adam Simpkins <adam@xxxxxxxxxxxxxxxx>
---
Documentation/technical/api-history-graph.txt | 176 +++++
Makefile | 2 +
graph.c | 903 +++++++++++++++++++++++++
graph.h | 121 ++++
4 files changed, 1202 insertions(+), 0 deletions(-)
create mode 100644 Documentation/technical/api-history-graph.txt
create mode 100644 graph.c
create mode 100644 graph.h
diff --git a/Documentation/technical/api-history-graph.txt b/Documentation/technical/api-history-graph.txt
new file mode 100644
index 0000000..5f6465f
--- /dev/null
+++ b/Documentation/technical/api-history-graph.txt
@@ -0,0 +1,176 @@
+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.
+
+Functions
+---------
+
+Core functions:
+
+* `graph_init()` creates a new `struct git_graph`
+
+* `graph_release()` destroys a `struct git_graph`, and frees the memory
+ associated with it.
+
+* `graph_update()` moves the graph to a new commit.
+
+* `graph_next_line()` outputs the next line of the graph into a strbuf. It
+ does not add a terminating newline.
+
+* `graph_padding_line()` outputs a line of vertical padding in the graph. It
+ is similar to `graph_next_line()`, but is guaranteed to never print the line
+ containing the current commit. Where `graph_next_line()` would print the
+ commit line next, `graph_padding_line()` prints a line that simply extends
+ all branch lines downwards one row, leaving their positions unchanged.
+
+* `graph_is_commit_finished()` determines if the graph has output all lines
+ necessary for the current commit. If `graph_update()` is called before all
+ lines for the current commit have been printed, the next call to
+ `graph_next_line()` will output an ellipsis, to indicate that a portion of
+ the graph was omitted.
+
+The following utility functions are wrappers around `graph_next_line()` and
+`graph_is_commit_finished()`. They always print the output to stdout.
+They can all be called with a NULL graph argument, in which case no graph
+output will be printed.
+
+* `graph_show_commit()` calls `graph_next_line()` until it returns non-zero.
+ This prints all graph lines up to, and including, the line containing this
+ commit. Output is printed to stdout. The last line printed does not contain
+ a terminating newline. This should not be called if the commit line has
+ already been printed, or it will loop forever.
+
+* `graph_show_oneline()` calls `graph_next_line()` and prints the result to
+ stdout. The line printed does not contain a terminating newline.
+
+* `graph_show_padding()` calls `graph_padding_line()` and prints the result to
+ stdout. The line printed does not contain a terminating newline.
+
+* `graph_show_remainder()` calls `graph_next_line()` until
+ `graph_is_commit_finished()` returns non-zero. Output is printed to stdout.
+ The last line printed does not contain a terminating newline. Returns 1 if
+ output was printed, and 0 if no output was necessary.
+
+* `graph_show_strbuf()` prints the specified strbuf to stdout, prefixing all
+ lines but the first with a graph line. The caller is responsible for
+ ensuring graph output for the first line has already been printed to stdout.
+ (This can be done with `graph_show_commit()` or `graph_show_oneline()`.) If
+ a NULL graph is supplied, the strbuf is printed as-is.
+
+* `graph_show_commit_msg()` is similar to `graph_show_strbuf()`, but it also
+ prints the remainder of the graph, if more lines are needed after the strbuf
+ ends. It is better than directly calling `graph_show_strbuf()` followed by
+ `graph_show_remainder()` since it properly handles buffers that do not end in
+ a terminating newline. The output printed by `graph_show_commit_msg()` will
+ end in a newline if and only if the strbuf ends in a newline.
+
+Data structure
+--------------
+`struct git_graph` is an opaque data type used to store the current graph
+state.
+
+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 traversed, call `graph_update()` to move the graph to the
+ next commit. Once `graph_update()` has been called, call `graph_next_line()`
+ repeatedly, until `graph_is_commit_finished()` returns non-zero. Each call
+ to `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.
+
+Limitations
+-----------
+
+* `graph_update()` must be called with commits in topological order. It should
+ not be called on a commit if it has already been invoked with an ancestor of
+ that commit, or the graph output will be incorrect.
+
+* `graph_update()` must be called on a contiguous group of commits. If
+ `graph_update()` is called on a particular commit, it should later be called
+ on all parents of that commit. Parents must not be skipped, or the graph
+ output will appear incorrect.
++
+`graph_update()` may be used on a pruned set of commits only if the parent list
+has been rewritten so as to include only ancestors from the pruned set.
+
+* 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 are responsible for
+outputting that information, if desired.
+
+------------
+*
+*
+M
+|\
+* |
+| | *
+| \ \
+| \ \
+M-. \ \
+|\ \ \ \
+| | * | |
+| | | | | *
+| | | | | *
+| | | | | M
+| | | | | |\
+| | | | | | *
+| * | | | | |
+| | | | | M \
+| | | | | |\ |
+| | | | * | | |
+| | | | * | | |
+* | | | | | | |
+| |/ / / / / /
+|/| / / / / /
+* | | | | | |
+|/ / / / / /
+* | | | | |
+| | | | | *
+| | | | |/
+| | | | *
+------------
diff --git a/Makefile b/Makefile
index 9d84c8d..d42b117 100644
--- a/Makefile
+++ b/Makefile
@@ -346,6 +346,7 @@ 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
@@ -411,6 +412,7 @@ 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
diff --git a/graph.c b/graph.c
new file mode 100644
index 0000000..b575d10
--- /dev/null
+++ b/graph.c
@@ -0,0 +1,903 @@
+#include "cache.h"
+#include "commit.h"
+#include "graph.h"
+#include "diff.h"
+#include "revision.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;
+
+ /*
+ * Ignore uinteresting and pruned commits
+ */
+ if (commit->object.flags & (UNINTERESTING | TREESAME))
+ return;
+
+ /*
+ * 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;
+ *mapping_index += 2;
+ 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;
+ *mapping_index += 2;
+ 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);
+ }
+ } else {
+ graph_insert_into_new_columns(graph, col_commit,
+ &mapping_idx);
+ }
+ }
+
+ /*
+ * 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;
+}
+
+void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
+{
+ int i, j;
+
+ 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 commit *col_commit = graph->columns[i].commit;
+ if (col_commit == graph->commit) {
+ strbuf_addch(sb, '|');
+
+ if (graph->num_parents < 3)
+ strbuf_addch(sb, ' ');
+ else {
+ int num_spaces = ((graph->num_parents - 2) * 2);
+ for (j = 0; j < num_spaces; j++)
+ strbuf_addch(sb, ' ');
+ }
+ } else {
+ strbuf_addstr(sb, "| ");
+ }
+ }
+
+ graph_pad_horizontally(graph, sb);
+}
+
+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;
+ int shown_commit_line = 0;
+
+ if (!graph)
+ return;
+
+ strbuf_init(&msgbuf, 0);
+
+ while (!shown_commit_line) {
+ shown_commit_line = graph_next_line(graph, &msgbuf);
+ fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
+ if (!shown_commit_line)
+ putchar('\n');
+ strbuf_setlen(&msgbuf, 0);
+ }
+
+ strbuf_release(&msgbuf);
+}
+
+void graph_show_oneline(struct git_graph *graph)
+{
+ struct strbuf msgbuf;
+
+ if (!graph)
+ return;
+
+ strbuf_init(&msgbuf, 0);
+ graph_next_line(graph, &msgbuf);
+ fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
+ strbuf_release(&msgbuf);
+}
+
+void graph_show_padding(struct git_graph *graph)
+{
+ struct strbuf msgbuf;
+
+ if (!graph)
+ return;
+
+ strbuf_init(&msgbuf, 0);
+ graph_padding_line(graph, &msgbuf);
+ fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
+ strbuf_release(&msgbuf);
+}
+
+int graph_show_remainder(struct git_graph *graph)
+{
+ struct strbuf msgbuf;
+ int shown = 0;
+
+ if (!graph)
+ return 0;
+
+ if (graph_is_commit_finished(graph))
+ return 0;
+
+ strbuf_init(&msgbuf, 0);
+ for (;;) {
+ graph_next_line(graph, &msgbuf);
+ fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
+ strbuf_setlen(&msgbuf, 0);
+ shown = 1;
+
+ if (!graph_is_commit_finished(graph))
+ putchar('\n');
+ else
+ break;
+ }
+ strbuf_release(&msgbuf);
+
+ return shown;
+}
+
+
+void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
+{
+ if (!graph) {
+ fwrite(sb->buf, sizeof(char), sb->len, stdout);
+ return;
+ }
+
+ /*
+ * Print the strbuf line by line,
+ * and display the graph info before each line but the first.
+ */
+ char *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, stdout);
+ if (next_p && *next_p != '\0')
+ graph_show_oneline(graph);
+ p = next_p;
+ }
+}
+
+void graph_show_commit_msg(struct git_graph *graph,
+ struct strbuf const *sb)
+{
+ if (!graph) {
+ /*
+ * If there's no graph, just print the message buffer.
+ *
+ * The message buffer for CMIT_FMT_ONELINE and
+ * CMIT_FMT_USERFORMAT are already missing a terminating
+ * newline. All of the other formats should have it.
+ */
+ fwrite(sb->buf, sizeof(char), sb->len, stdout);
+ return;
+ }
+
+ int newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
+
+ /*
+ * Show the commit message
+ */
+ graph_show_strbuf(graph, sb);
+
+ /*
+ * 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)
+ putchar('\n');
+
+ graph_show_remainder(graph);
+
+ /*
+ * If sb ends with a newline, our output should too.
+ */
+ if (newline_terminated)
+ putchar('\n');
+ }
+}
diff --git a/graph.h b/graph.h
new file mode 100644
index 0000000..a7748a5
--- /dev/null
+++ b/graph.h
@@ -0,0 +1,121 @@
+#ifndef GRAPH_H
+#define GRAPH_H
+
+/* A graph is a pointer to this opaque structure */
+struct git_graph;
+
+/*
+ * Create a new struct git_graph.
+ * The graph should be freed with graph_release() when no longer needed.
+ */
+struct git_graph *graph_init();
+
+/*
+ * Destroy a struct git_graph and free associated memory.
+ */
+void graph_release(struct git_graph *graph);
+
+/*
+ * Update a git_graph with a new commit.
+ * This will cause the graph to begin outputting lines for the new commit
+ * the next time graph_next_line() is called.
+ *
+ * If graph_update() is called before graph_is_commit_finished() returns 1,
+ * the next call to graph_next_line() will output an ellipsis ("...")
+ * to indicate that a portion of the graph is missing.
+ */
+void graph_update(struct git_graph *graph, struct commit *commit);
+
+/*
+ * Output the next line for a graph.
+ * This formats the next graph line into the specified strbuf. It is not
+ * terminated with a newline.
+ *
+ * Returns 1 if the line includes the current commit, and 0 otherwise.
+ * graph_next_line() will return 1 exactly once for each time
+ * graph_update() is called.
+ */
+int graph_next_line(struct git_graph *graph, struct strbuf *sb);
+
+/*
+ * 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.
+ */
+void graph_padding_line(struct git_graph *graph, struct strbuf *sb);
+
+/*
+ * Determine if a graph has finished outputting lines for the current
+ * commit.
+ *
+ * Returns 1 if graph_next_line() needs to be called again before
+ * graph_update() should be called. Returns 0 if no more lines are needed
+ * for this commit. If 0 is returned, graph_next_line() may still be
+ * called without calling graph_update(), and it will merely output
+ * appropriate "vertical padding" in the graph.
+ */
+int graph_is_commit_finished(struct git_graph const *graph);
+
+
+/*
+ * graph_show_*: helper functions for printing to stdout
+ */
+
+
+/*
+ * If the graph is non-NULL, print the history graph to stdout,
+ * up to and including the line containing this commit.
+ * Does not print a terminating newline on the last line.
+ */
+void graph_show_commit(struct git_graph *graph);
+
+/*
+ * If the graph is non-NULL, print one line of the history graph to stdout.
+ * Does not print a terminating newline on the last line.
+ */
+void graph_show_oneline(struct git_graph *graph);
+
+/*
+ * If the graph is non-NULL, print one line of vertical graph padding to
+ * stdout. Does not print a terminating newline on the last line.
+ */
+void graph_show_padding(struct git_graph *graph);
+
+/*
+ * If the graph is non-NULL, print the rest of the history graph for this
+ * commit to stdout. Does not print a terminating newline on the last line.
+ */
+int graph_show_remainder(struct git_graph *graph);
+
+/*
+ * Print a strbuf to stdout. 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 ouput, the caller is
+ * responsible for printing this line's graph (perhaps via
+ * graph_show_commit() or graph_show_oneline()) before calling
+ * graph_show_strbuf().
+ */
+void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb);
+
+/*
+ * Print a commit message strbuf and the remainder of the graph to stdout.
+ *
+ * This is similar to graph_show_strbuf(), but it always prints the
+ * remainder of the graph.
+ *
+ * If the strbuf ends with a newline, the output printed by
+ * graph_show_commit_msg() will end with a newline. If the strbuf is
+ * missing a terminating newline (including if it is empty), the output
+ * printed by graph_show_commit_msg() will also be missing a terminating
+ * newline.
+ */
+void graph_show_commit_msg(struct git_graph *graph, struct strbuf const *sb);
+
+#endif /* GRAPH_H */
--
1.5.5.1.128.gc15ea
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