1 files changed, 26 insertions, 6 deletions

diff --git a/patch-ids.c b/patch-ids.c
index 69a14a3b50..082412aca6 100644
--- a/patch-ids.c
+++ b/patch-ids.c
@@ -5,7 +5,7 @@
 #include "patch-ids.h"
 
 int commit_patch_id(struct commit *commit, struct diff_options *options,
-		    unsigned char *sha1)
+		    unsigned char *sha1, int diff_header_only)
 {
 	if (commit->parents)
 		diff_tree_sha1(commit->parents->item->object.oid.hash,
@@ -13,13 +13,31 @@ int commit_patch_id(struct commit *commit, struct diff_options *options,
 	else
 		diff_root_tree_sha1(commit->object.oid.hash, "", options);
 	diffcore_std(options);
-	return diff_flush_patch_id(options, sha1, 0);
+	return diff_flush_patch_id(options, sha1, diff_header_only);
 }
 
+/*
+ * When we cannot load the full patch-id for both commits for whatever
+ * reason, the function returns -1 (i.e. return error(...)). Despite
+ * the "cmp" 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_cmp(struct patch_id *a,
 			struct patch_id *b,
-			void *keydata)
+			struct diff_options *opt)
 {
+	if (is_null_sha1(a->patch_id) &&
+	    commit_patch_id(a->commit, opt, a->patch_id, 0))
+		return error("Could not get patch ID for %s",
+			oid_to_hex(&a->commit->object.oid));
+	if (is_null_sha1(b->patch_id) &&
+	    commit_patch_id(b->commit, opt, b->patch_id, 0))
+		return error("Could not get patch ID for %s",
+			oid_to_hex(&b->commit->object.oid));
 	return hashcmp(a->patch_id, b->patch_id);
 }
 
@@ -43,11 +61,13 @@ static int init_patch_id_entry(struct patch_id *patch,
 			       struct commit *commit,
 			       struct patch_ids *ids)
 {
+	unsigned char header_only_patch_id[GIT_SHA1_RAWSZ];
+
 	patch->commit = commit;
-	if (commit_patch_id(commit, &ids->diffopts, patch->patch_id))
+	if (commit_patch_id(commit, &ids->diffopts, header_only_patch_id, 1))
 		return -1;
 
-	hashmap_entry_init(patch, sha1hash(patch->patch_id));
+	hashmap_entry_init(patch, sha1hash(header_only_patch_id));
 	return 0;
 }
 
@@ -60,7 +80,7 @@ struct patch_id *has_commit_patch_id(struct commit *commit,
 	if (init_patch_id_entry(&patch, commit, ids))
 		return NULL;
 
-	return hashmap_get(&ids->patches, &patch, NULL);
+	return hashmap_get(&ids->patches, &patch, &ids->diffopts);
 }
 
 struct patch_id *add_commit_patch_id(struct commit *commit,