On 2/21/2018 6:13 PM, Jeff King wrote:
On Wed, Feb 21, 2018 at 02:17:11PM -0500, Derrick Stolee wrote:
The get_cached_commit_buffer() method provides access to the buffer
loaded for a struct commit, if it was ever loadead and was not freed.
Two places use this to inform how to output information about commits.
log-tree.c uses this method to short-circuit the output of commit
information when the buffer is not cached. However, this leads to
incorrect output in 'git log --oneline' where the short-OID is written
but then the rest of the commit information is dropped and the next
commit is written on the same line.
rev-list uses this method for two reasons:
- First, if the revision walk visits a commit twice, the buffer was
freed by rev-list in the first write. The output then does not
match the format expectations, since the OID is written without the
rest of the content.
I'm not sure after my earlier digging if there is even a way to trigger
this (and if so, it is probably accidental, since those lines were added
explicitly for --show-all).
And actually after re-reading the commit message for 3131b7130 again, I
think the current behavior is definitely not something that was
carefully planned. So I'd propose a commit message like below.
I only submitted my patch to avoid making you do the work of writing the
commit message. My messages still don't have quite the right amount of
detail (or the correct details, in this case).
Junio: please add
Reported-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
Thanks,
-Stolee
-- >8 --
Subject: [PATCH] commit: drop uses of get_cached_commit_buffer()
The "--show-all" revision option shows UNINTERESTING
commits. Some of these commits may be unparsed when we try
to show them (since we may or may not need to walk their
parents to fulfill the request).
Commit 3131b71301 (Add "--show-all" revision walker flag for
debugging, 2008-02-09) resolved this by just skipping
pretty-printing for commits without their object contents
cached, saying:
Because we now end up listing commits we may not even have been parsed
at all "show_log" and "show_commit" need to protect against commits
that don't have a commit buffer entry.
That was the easy fix to avoid the pretty-printer segfaulting,
but:
1. It doesn't work for all formats. E.g., --oneline
prints the oid for each such commit but not a trailing
newline, leading to jumbled output.
2. It only affects some commits, depending on whether we
happened to parse them or not (so if they were at the
tip of an UNINTERESTING starting point, or if we
happened to traverse over them, you'd see more data).
3. It unncessarily ties the decision to show the verbose
header to whether the commit buffer was cached. That
makes it harder to change the logic around caching
(e.g., if we could traverse without actually loading
the full commit objects).
These days it's safe to feed such a commit to the
pretty-print code. Since be5c9fb904 (logmsg_reencode: lazily
load missing commit buffers, 2013-01-26), we'll load it on
demand in such a case. So let's just always show the verbose
headers.
This does change the behavior of plumbing, but:
a. The --show-all option was explicitly introduced as a
debugging aid, and was never documented (and has rarely
even been mentioned on the list by git devs).
b. Avoiding the commits was already not deterministic due
to (2) above. So the caller might have seen full
headers for these commits anyway, and would need to be
prepared for it.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
builtin/rev-list.c | 2 +-
log-tree.c | 3 ---
2 files changed, 1 insertion(+), 4 deletions(-)
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 48300d9e11..d320b6f1e3 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -134,7 +134,7 @@ static void show_commit(struct commit *commit, void *data)
else
putchar('\n');
- if (revs->verbose_header && get_cached_commit_buffer(commit, NULL)) {
+ if (revs->verbose_header) {
struct strbuf buf = STRBUF_INIT;
struct pretty_print_context ctx = {0};
ctx.abbrev = revs->abbrev;
diff --git a/log-tree.c b/log-tree.c
index fc0cc0d6d1..22b2fb6c58 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -659,9 +659,6 @@ void show_log(struct rev_info *opt)
show_mergetag(opt, commit);
}
- if (!get_cached_commit_buffer(commit, NULL))
- return;
-
if (opt->show_notes) {
int raw;
struct strbuf notebuf = STRBUF_INIT;
