log: avoid loading decorations for userformats that don't need it

peff · gitster · commit b2086b518366 · 2021-06-28T20:30:17.000-07:00
If no --decorate option is given, we default to auto-decoration. And
when that kicks in, cmd_log_init_finish() will unconditionally load the
decoration refs.

However, if we are using a user-format that does not include "%d" or
"%D", we won't show the decorations at all, so we don't need to load
them. We can detect this case and auto-disable them by adding a new
field to our userformat_want helper. We can do this even when the user
explicitly asked for --decorate, because it can't affect the output at
all.

This patch consistently reduces the time to run "git log -1 --format=%H"
on my git.git clone (with ~2k refs) from 34ms to 7ms. On a much more
extreme real-world repository (with ~220k refs), it goes from 2.5s to
4ms.

Signed-off-by: Jeff King &lt;peff@peff.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/builtin/log.c b/builtin/log.c
@@ -245,6 +245,9 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 			rev->abbrev_commit = 0;
 	}
 
+	if (rev->commit_format == CMIT_FMT_USERFORMAT && !w.decorate)
+		decoration_style = 0;
+
 	if (decoration_style) {
 		const struct string_list *config_exclude =
 			repo_config_get_value_multi(the_repository,
diff --git a/pretty.c b/pretty.c
@@ -1735,6 +1735,10 @@ static size_t userformat_want_item(struct strbuf *sb, const char *placeholder,
 	case 'S':
 		w->source = 1;
 		break;
+	case 'd':
+	case 'D':
+		w->decorate = 1;
+		break;
 	}
 	return 0;
 }
diff --git a/pretty.h b/pretty.h
@@ -73,6 +73,7 @@ static inline int cmit_fmt_is_mail(enum cmit_fmt fmt)
 struct userformat_want {
 	unsigned notes:1;
 	unsigned source:1;
+	unsigned decorate:1;
 };
 void userformat_find_requirements(const char *fmt, struct userformat_want *w);
 

Original file line number	Diff line number	Diff line change
`@@ -245,6 +245,9 @@ static void cmd_log_init_finish(int argc, const char *argv, const char prefix,`
`245`	`245`	`rev->abbrev_commit = 0;`
`246`	`246`	`}`
`247`	`247`
	`248`	`+ if (rev->commit_format == CMIT_FMT_USERFORMAT && !w.decorate)`
	`249`	`+ decoration_style = 0;`
	`250`	`+`
`248`	`251`	`if (decoration_style) {`
`249`	`252`	`const struct string_list *config_exclude =`
`250`	`253`	`repo_config_get_value_multi(the_repository,`
Original file line number	Diff line number	Diff line change
`@@ -1735,6 +1735,10 @@ static size_t userformat_want_item(struct strbuf sb, const char placeholder,`
`1735`	`1735`	`case 'S':`
`1736`	`1736`	`w->source = 1;`
`1737`	`1737`	`break;`
	`1738`	`+ case 'd':`
	`1739`	`+ case 'D':`
	`1740`	`+ w->decorate = 1;`
	`1741`	`+ break;`
`1738`	`1742`	`}`
`1739`	`1743`	`return 0;`
`1740`	`1744`	`}`