1 files changed, 121 insertions, 0 deletions
diff --git a/patch-ids.c b/patch-ids.c
new file mode 100644
index 000000000000..e8c150d0c92a
--- /dev/null
+++ b/patch-ids.c
@@ -0,0 +1,121 @@
+#include "cache.h"
+#include "diff.h"
+#include "commit.h"
+#include "sha1-lookup.h"
+#include "patch-ids.h"
+
+static int patch_id_defined(struct commit *commit)
+{
+	/* must be 0 or 1 parents */
+	return !commit->parents || !commit->parents->next;
+}
+
+int commit_patch_id(struct commit *commit, struct diff_options *options,
+		    struct object_id *oid, int diff_header_only, int stable)
+{
+	if (!patch_id_defined(commit))
+		return -1;
+
+	if (commit->parents)
+		diff_tree_oid(&commit->parents->item->object.oid,
+			      &commit->object.oid, "", options);
+	else
+		diff_root_tree_oid(&commit->object.oid, "", options);
+	diffcore_std(options);
+	return diff_flush_patch_id(options, oid, diff_header_only, stable);
+}
+
+/*
+ * When we cannot load the full patch-id for both commits for whatever
+ * reason, the function returns -1 (i.e. return error(...)). Despite
+ * the "neq" in the name of this function, the caller only cares about
+ * the return value being zero (a and b are equivalent) or non-zero (a
+ * and b are different), and returning non-zero would keep both in the
+ * result, even if they actually were equivalent, in order to err on
+ * the side of safety.  The actual value being negative does not have
+ * any significance; only that it is non-zero matters.
+ */
+static int patch_id_neq(const void *cmpfn_data,
+			const void *entry,
+			const void *entry_or_key,
+			const void *unused_keydata)
+{
+	/* NEEDSWORK: const correctness? */
+	struct diff_options *opt = (void *)cmpfn_data;
+	struct patch_id *a = (void *)entry;
+	struct patch_id *b = (void *)entry_or_key;
+
+	if (is_null_oid(&a->patch_id) &&
+	    commit_patch_id(a->commit, opt, &a->patch_id, 0, 0))
+		return error("Could not get patch ID for %s",
+			oid_to_hex(&a->commit->object.oid));
+	if (is_null_oid(&b->patch_id) &&
+	    commit_patch_id(b->commit, opt, &b->patch_id, 0, 0))
+		return error("Could not get patch ID for %s",
+			oid_to_hex(&b->commit->object.oid));
+	return !oideq(&a->patch_id, &b->patch_id);
+}
+
+int init_patch_ids(struct repository *r, struct patch_ids *ids)
+{
+	memset(ids, 0, sizeof(*ids));
+	repo_diff_setup(r, &ids->diffopts);
+	ids->diffopts.detect_rename = 0;
+	ids->diffopts.flags.recursive = 1;
+	diff_setup_done(&ids->diffopts);
+	hashmap_init(&ids->patches, patch_id_neq, &ids->diffopts, 256);
+	return 0;
+}
+
+int free_patch_ids(struct patch_ids *ids)
+{
+	hashmap_free(&ids->patches, 1);
+	return 0;
+}
+
+static int init_patch_id_entry(struct patch_id *patch,
+			       struct commit *commit,
+			       struct patch_ids *ids)
+{
+	struct object_id header_only_patch_id;
+
+	patch->commit = commit;
+	if (commit_patch_id(commit, &ids->diffopts, &header_only_patch_id, 1, 0))
+		return -1;
+
+	hashmap_entry_init(patch, oidhash(&header_only_patch_id));
+	return 0;
+}
+
+struct patch_id *has_commit_patch_id(struct commit *commit,
+				     struct patch_ids *ids)
+{
+	struct patch_id patch;
+
+	if (!patch_id_defined(commit))
+		return NULL;
+
+	memset(&patch, 0, sizeof(patch));
+	if (init_patch_id_entry(&patch, commit, ids))
+		return NULL;
+
+	return hashmap_get(&ids->patches, &patch, NULL);
+}
+
+struct patch_id *add_commit_patch_id(struct commit *commit,
+				     struct patch_ids *ids)
+{
+	struct patch_id *key;
+
+	if (!patch_id_defined(commit))
+		return NULL;
+
+	key = xcalloc(1, sizeof(*key));
+	if (init_patch_id_entry(key, commit, ids)) {
+		free(key);
+		return NULL;
+	}
+
+	hashmap_add(&ids->patches, key);
+	return key;
+}