[PATCH v2 2/5] notes: avoid launching a child process to show a note blob

[Maarten Bosmans <mkbosmans@gmail.com>]

From: Maarten Bosmans <mkbosmans@gmail.com>

From: Maarten Bosmans <maarten.bosmans@vortech.nl>

Avoid the need to launch a subprocess by calling stream_blob_to_fd
directly.  This does not only get rid of the overhead of a separate
child process, but also avoids the initalization of the whole log
machinery that `git show` does.  That is needed for example to show
decorated commits and applying the mailmap.  For simply displaying
a blob however, the only useful thing show does is enabling the pager.

This locks in the expectation that a note oid refers to a blob, and
not a tree or something else.  To still keep the option open that the
blob might not be a text blob and in the future we might handle such
notes differently, the show_blob_object() function is called in order
to have the same behaviour as though `git show <note-oid>` was called.

Signed-off-by: Maarten Bosmans <maarten.bosmans@vortech.nl>
---
 builtin/notes.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/builtin/notes.c b/builtin/notes.c
index caf20fd5bd..2a31da6c97 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -20,7 +20,8 @@
 #include "repository.h"
 #include "pretty.h"
 #include "refs.h"
-#include "exec-cmd.h"
+#include "pager.h"
+#include "log.h"
 #include "run-command.h"
 #include "parse-options.h"
 #include "string-list.h"
@@ -753,7 +754,7 @@ static int show(int argc, const char **argv, const char *prefix)
 	struct notes_tree *t;
 	struct object_id object;
 	const struct object_id *note;
-	int retval;
+	int retval = 0;
 	struct option options[] = {
 		OPT_END()
 	};
@@ -778,8 +779,9 @@ static int show(int argc, const char **argv, const char *prefix)
 		retval = error(_("no note found for object %s."),
 			       oid_to_hex(&object));
 	else {
-		const char *show_args[3] = {"show", oid_to_hex(note), NULL};
-		retval = execv_git_cmd(show_args);
+		setup_pager();
+		if (show_blob_object(note, NULL, false))
+			die(_("object %s is not a blob"), oid_to_hex(note));
 	}
 	free_notes(t);
 	return retval;
-- 
2.35.3