graph: Create `git_graph_reachable_from_any()`

This change introduces a new API function
`git_graph_reachable_from_any()`, that answers the question whether a
commit is reachable from any of the provided commits through following
parent edges.

This function can take advantage of optimizations provided by the
existence of a `commit-graph` file, since it makes it faster to know
whether, given two commits X and Y, X cannot possibly be an reachable
from Y.

Part of: #5757

1 files changed, 20 insertions, 2 deletions

diff --git a/include/git2/graph.h b/include/git2/graph.h
index 213ae9777..cd4897fef 100644
--- a/include/git2/graph.h
+++ b/include/git2/graph.h
@@ -43,8 +43,9 @@ GIT_EXTERN(int) git_graph_ahead_behind(size_t *ahead, size_t *behind, git_reposi
  * Note that a commit is not considered a descendant of itself, in contrast
  * to `git merge-base --is-ancestor`.
  *
- * @param commit a previously loaded commit.
- * @param ancestor a potential ancestor commit.
+ * @param repo the repository where the commits exist
+ * @param commit a previously loaded commit
+ * @param ancestor a potential ancestor commit
  * @return 1 if the given commit is a descendant of the potential ancestor,
  * 0 if not, error code otherwise.
  */
@@ -53,6 +54,23 @@ GIT_EXTERN(int) git_graph_descendant_of(
 	const git_oid *commit,
 	const git_oid *ancestor);
 
+/**
+ * Determine if a commit is reachable from any of a list of commits by
+ * following parent edges.
+ *
+ * @param repo the repository where the commits exist
+ * @param commit a previously loaded commit
+ * @param length the number of commits in the provided `descendant_array`
+ * @param descendant_array oids of the commits
+ * @return 1 if the given commit is an ancestor of any of the given potential
+ * descendants, 0 if not, error code otherwise.
+ */
+GIT_EXTERN(int) git_graph_reachable_from_any(
+	git_repository *repo,
+	const git_oid *commit,
+	size_t length,
+	const git_oid descendant_array[]);
+
 /** @} */
 GIT_END_DECL
 #endif