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-rw-r--r--graph.h121
1 files changed, 121 insertions, 0 deletions
diff --git a/graph.h b/graph.h
index af623390b6..8313e293c7 100644
--- a/graph.h
+++ b/graph.h
@@ -2,6 +2,103 @@
#define GRAPH_H
#include "diff.h"
+/**
+ * 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()`. When using the
+ * revision walking API, this is done automatically by `setup_revisions()` if
+ * the '--graph' option is supplied.
+ *
+ * - Use the revision walking API to walk through a group of contiguous commits.
+ * The `get_revision()` function automatically calls `graph_update()` each time
+ * it is invoked.
+ *
+ * - For each commit, 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
+ * -----------
+ * - Check the graph_update() function for its limitations.
+ *
+ * - 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(opts);
+ *
+ * while ((commit = get_revision(opts)) != NULL) {
+ * 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);
+ * }
+ * }
+ * ------------
+ * 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.
+ * ------------
+ * *
+ * *
+ * *
+ * |\
+ * * |
+ * | | *
+ * | \ \
+ * | \ \
+ * *-. \ \
+ * |\ \ \ \
+ * | | * | |
+ * | | | | | *
+ * | | | | | *
+ * | | | | | *
+ * | | | | | |\
+ * | | | | | | *
+ * | * | | | | |
+ * | | | | | * \
+ * | | | | | |\ |
+ * | | | | * | | |
+ * | | | | * | | |
+ * * | | | | | | |
+ * | |/ / / / / /
+ * |/| / / / / /
+ * * | | | | | |
+ * |/ / / / / /
+ * * | | | | |
+ * | | | | | *
+ * | | | | |/
+ * | | | | *
+ * ------------
+ *
+ */
+
/* A graph is a pointer to this opaque structure */
struct git_graph;
@@ -50,6 +147,21 @@ struct git_graph *graph_init(struct rev_info *opt);
* 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.
+ *
+ * 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.
*/
void graph_update(struct git_graph *graph, struct commit *commit);
@@ -62,6 +174,10 @@ void graph_update(struct git_graph *graph, struct commit *commit);
* 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.
+ *
+ * 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.
*/
int graph_is_commit_finished(struct git_graph const *graph);
@@ -112,6 +228,7 @@ 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.
+ * Returns 1 if output was printed, and 0 if no output was necessary.
*/
int graph_show_remainder(struct git_graph *graph);
@@ -121,6 +238,10 @@ int graph_show_remainder(struct git_graph *graph);
* This is similar to graph_show_strbuf(), but it always prints the
* remainder of the graph.
*
+ * 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.
+ *
* 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