Pass an already open commit object to the blame callback.
This was written on top of my id_by_path diff I sent earlier.

The idea is to avoid re-opening the same commit again in the blame callback
as implemented by got.c and gotweb.c. Otherwise, these callbacks rely on the
commit cache to avoid doing the same amount of work the caller already did.

ok?
 
diff 6fd1a33c932d168a9aef98ca7760e8f63446bea1 43acb5b55df6240c091bc4ec11079eaee47d64a7
blob - 7ac9d84ea1bc903f4fd7ab569799630bbaa48aaa
blob + 1b4824dc3a8b72c725ef07b0e5d942bb8ad41589
--- got/got.c
+++ got/got.c
@@ -4876,14 +4876,14 @@ struct blame_cb_args {
 };
 
 static const struct got_error *
-blame_cb(void *arg, int nlines, int lineno, struct got_object_id *id)
+blame_cb(void *arg, int nlines, int lineno,
+    struct got_commit_object *commit, struct got_object_id *id)
 {
 	const struct got_error *err = NULL;
 	struct blame_cb_args *a = arg;
 	struct blame_line *bline;
 	char *line = NULL;
 	size_t linesize = 0;
-	struct got_commit_object *commit = NULL;
 	off_t offset;
 	struct tm tm;
 	time_t committer_time;
@@ -4906,10 +4906,6 @@ blame_cb(void *arg, int nlines, int lineno, struct got
 	if (err)
 		return err;
 
-	err = got_object_open_as_commit(&commit, a->repo, id);
-	if (err)
-		goto done;
-
 	bline->committer = strdup(got_object_commit_get_committer(commit));
 	if (bline->committer == NULL) {
 		err = got_error_from_errno("strdup");
@@ -4968,8 +4964,6 @@ blame_cb(void *arg, int nlines, int lineno, struct got
 		bline = &a->lines[a->lineno_cur - 1];
 	}
 done:
-	if (commit)
-		got_object_commit_close(commit);
 	free(line);
 	return err;
 }
blob - 70b31ef68737cdd0d46bd944fea3af2c33d3e89a
blob + 710788181588ea0542eb1b6312476ddaa579fc99
--- gotweb/gotweb.c
+++ gotweb/gotweb.c
@@ -214,6 +214,7 @@ static const struct got_error	*gw_get_commit(struct gw
 				    struct got_object_id *);
 static const struct got_error	*gw_apply_unveil(const char *);
 static const struct got_error	*gw_blame_cb(void *, int, int,
+				    struct got_commit_object *,
 				    struct got_object_id *);
 static const struct got_error	*gw_load_got_paths(struct gw_trans *);
 static const struct got_error	*gw_load_got_path(struct gw_trans *,
@@ -3862,14 +3863,14 @@ struct gw_blame_cb_args {
 };
 
 static const struct got_error *
-gw_blame_cb(void *arg, int nlines, int lineno, struct got_object_id *id)
+gw_blame_cb(void *arg, int nlines, int lineno,
+    struct got_commit_object *commit, struct got_object_id *id)
 {
 	const struct got_error *err = NULL;
 	struct gw_blame_cb_args *a = arg;
 	struct blame_line *bline;
 	char *line = NULL;
 	size_t linesize = 0;
-	struct got_commit_object *commit = NULL;
 	off_t offset;
 	struct tm tm;
 	time_t committer_time;
@@ -3890,10 +3891,6 @@ gw_blame_cb(void *arg, int nlines, int lineno, struct 
 	if (err)
 		return err;
 
-	err = got_object_open_as_commit(&commit, a->repo, id);
-	if (err)
-		goto done;
-
 	bline->committer = strdup(got_object_commit_get_committer(commit));
 	if (bline->committer == NULL) {
 		err = got_error_from_errno("strdup");
@@ -4030,8 +4027,6 @@ err:
 		free(href_diff);
 	}
 done:
-	if (commit)
-		got_object_commit_close(commit);
 	free(line);
 	if (err == NULL && kerr != KCGI_OK)
 		err = gw_kcgi_error(kerr);
blob - c4c15ba2906056d4efdd0378fb21aa0e70cf83f7
blob + e360955ca287d181a8ff24dbf66100470e96de18
--- include/got_blame.h
+++ include/got_blame.h
@@ -14,6 +14,9 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+typedef const struct got_error *(*got_blame_cb)(void *, int, int,
+    struct got_commit_object *, struct got_object_id *);
+
 /*
  * Blame the blob at the specified path in the specified commit and invoke
  * a callback whenever an annotation has been computed for a line.
@@ -33,5 +36,4 @@
  */
 const struct got_error *got_blame(const char *,
     struct got_object_id *, struct got_repository *,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *, got_cancel_cb, void *);
+    got_blame_cb, void *, got_cancel_cb, void *);
blob - 4fb57b680144beb72b8bb8898b73e6d032ad15d8
blob + 19208f0e07660099d682daaab42dfacd9c2c5724
--- lib/blame.c
+++ lib/blame.c
@@ -89,9 +89,9 @@ struct got_blame {
 };
 
 static const struct got_error *
-annotate_line(struct got_blame *blame, int lineno, struct got_object_id *id,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *arg)
+annotate_line(struct got_blame *blame, int lineno,
+    struct got_commit_object *commit, struct got_object_id *id,
+    got_blame_cb cb, void *arg)
 {
 	const struct got_error *err = NULL;
 	struct got_blame_line *line;
@@ -107,15 +107,14 @@ annotate_line(struct got_blame *blame, int lineno, str
 	line->annotated = 1;
 	blame->nannotated++;
 	if (cb)
-		err = cb(arg, blame->nlines, lineno + 1, id);
+		err = cb(arg, blame->nlines, lineno + 1, commit, id);
 	return err;
 }
 
 static const struct got_error *
 blame_changes(struct got_blame *blame, struct diff_result *diff_result,
-    struct got_object_id *commit_id,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *arg)
+    struct got_commit_object *commit, struct got_object_id *commit_id,
+    got_blame_cb cb, void *arg)
 {
 	const struct got_error *err = NULL;
 	int i;
@@ -153,7 +152,8 @@ blame_changes(struct got_blame *blame, struct diff_res
 
 		for (j = 0; j < right_count; j++) {
 			int ln = blame->linemap2[idx2++];
-			err = annotate_line(blame, ln, commit_id, cb, arg);
+			err = annotate_line(blame, ln, commit, commit_id,
+			    cb, arg);
 			if (err)
 				return err;
 			if (blame->nlines == blame->nannotated)
@@ -196,8 +196,7 @@ blame_prepare_file(FILE *f, unsigned char **p, off_t *
 static const struct got_error *
 blame_commit(struct got_blame *blame, struct got_object_id *id,
     const char *path, struct got_repository *repo,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *arg)
+    got_blame_cb cb, void *arg)
 {
 	const struct got_error *err = NULL;
 	struct got_commit_object *commit = NULL, *pcommit = NULL;
@@ -261,11 +260,11 @@ blame_commit(struct got_blame *blame, struct got_objec
 				goto done;
 			}
 		}
-		err = blame_changes(blame, diff_result, id, cb, arg);
+		err = blame_changes(blame, diff_result, commit, id, cb, arg);
 		if (err)
 			goto done;
 	} else if (cb)
-		err = cb(arg, blame->nlines, -1, id);
+		err = cb(arg, blame->nlines, -1, commit, id);
 done:
 	if (diff_result)
 		diff_result_free(diff_result);
@@ -500,11 +499,10 @@ close_file2_and_reuse_file1(struct got_blame *blame)
 static const struct got_error *
 blame_open(struct got_blame **blamep, const char *path,
     struct got_object_id *start_commit_id, struct got_repository *repo,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *arg, got_cancel_cb cancel_cb, void *cancel_arg)
+    got_blame_cb cb, void *arg, got_cancel_cb cancel_cb, void *cancel_arg)
 {
 	const struct got_error *err = NULL;
-	struct got_commit_object *start_commit = NULL;
+	struct got_commit_object *start_commit = NULL, *last_commit = NULL;
 	struct got_object_id *obj_id = NULL;
 	struct got_blob_object *blob = NULL;
 	struct got_blame *blame = NULL;
@@ -619,8 +617,12 @@ blame_open(struct got_blame **blamep, const char *path
 
 	if (id && blame->nannotated < blame->nlines) {
 		/* Annotate remaining non-annotated lines with last commit. */
+		err = got_object_open_as_commit(&last_commit, repo, id);
+		if (err)
+			goto done;
 		for (lineno = 0; lineno < blame->nlines; lineno++) {
-			err = annotate_line(blame, lineno, id, cb, arg);
+			err = annotate_line(blame, lineno, last_commit, id,
+			    cb, arg);
 			if (err)
 				goto done;
 		}
@@ -634,6 +636,8 @@ done:
 		got_object_blob_close(blob);
 	if (start_commit)
 		got_object_commit_close(start_commit);
+	if (last_commit)
+		got_object_commit_close(last_commit);
 	if (err) {
 		if (blame)
 			blame_close(blame);
@@ -645,9 +649,8 @@ done:
 
 const struct got_error *
 got_blame(const char *path, struct got_object_id *commit_id,
-    struct got_repository *repo,
-    const struct got_error *(*cb)(void *, int, int, struct got_object_id *),
-    void *arg, got_cancel_cb cancel_cb, void* cancel_arg)
+    struct got_repository *repo, got_blame_cb cb, void *arg,
+    got_cancel_cb cancel_cb, void* cancel_arg)
 {
 	const struct got_error *err = NULL, *close_err = NULL;
 	struct got_blame *blame;
blob - cf640001b1d644e38bc4909d42362dd3ed7f348e
blob + 1235f3d15f5c154123999f3791ee35c3119cd238
--- tog/tog.c
+++ tog/tog.c
@@ -4162,7 +4162,8 @@ draw_blame(struct tog_view *view)
 }
 
 static const struct got_error *
-blame_cb(void *arg, int nlines, int lineno, struct got_object_id *id)
+blame_cb(void *arg, int nlines, int lineno,
+    struct got_commit_object *commit, struct got_object_id *id)
 {
 	const struct got_error *err = NULL;
 	struct tog_blame_cb_args *a = arg;