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

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 <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/log.c b/builtin/log.c
index 6102893..6ba7f20 100644 (file)
--- 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
index b1ecd03..9631529 100644 (file)
--- 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
index c81cf40..2f16acd 100644 (file)
--- 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);