8260bc5902
The --follow code doesn't handle most forms of pathspec magic. We check
that no unexpected ones have made it to try_to_follow_renames() with a
runtime GUARD_PATHSPEC() check, which gives behavior like this:
$ git log --follow ':(icase)makefile' >/dev/null
BUG: tree-diff.c:596: unsupported magic 10
Aborted
The same is true of ":(glob)", ":(attr)", and so on. It's good that we
notice the problem rather than continuing and producing a wrong answer.
But there are two non-ideal things:
1. The idea of GUARD_PATHSPEC() is to catch programming errors where
low-level code gets unexpected pathspecs. We'd usually try to catch
unsupported pathspecs by passing a magic_mask to parse_pathspec(),
which would give the user a much better message like:
pathspec magic not supported by this command: 'icase'
That doesn't happen here because git-log usually _does_ support
all types of pathspec magic, and so it passes "0" for the mask
(this call actually happens in setup_revisions()). It needs to
distinguish the normal case from the "--follow" one but currently
doesn't.
2. In addition to --follow, we have the log.follow config option. When
that is set, we try to turn on --follow mode only when there is a
single pathspec (since --follow doesn't handle anything else). But
really, that ought to be expanded to "use --follow when the
pathspec supports it". Otherwise, we'd complain any time you use an
exotic pathspec:
$ git config log.follow true
$ git log ':(icase)makefile' >/dev/null
BUG: tree-diff.c:596: unsupported magic 10
Aborted
We should instead just avoid enabling follow mode if it's not
supported by this particular invocation.
This patch expands our diff_check_follow_pathspec() function to cover
pathspec magic, solving both problems.
A few final notes:
- we could also solve (1) by passing the appropriate mask to
parse_pathspec(). But that's not great for two reasons. One is that
the error message is less precise. It says "magic not supported by
this command", but really it is not the command, but rather the
--follow option which is the problem. The second is that it always
calls die(). But for our log.follow code, we want to speculatively
ask "is this pathspec OK?" and just get a boolean result.
- This is obviously the right thing to do for ':(icase)' and most
other magic options. But ':(glob)' is a bit odd here. The --follow
code doesn't support wildcards, but we allow them anyway. From
try_to_follow_renames():
#if 0
/*
* We should reject wildcards as well. Unfortunately we
* haven't got a reliable way to detect that 'foo\*bar' in
* fact has no wildcards. nowildcard_len is merely a hint for
* optimization. Let it slip for now until wildmatch is taught
* about dry-run mode and returns wildcard info.
*/
if (opt->pathspec.has_wildcard)
BUG("wildcards are not supported");
#endif
So something like "git log --follow 'Make*'" is already doing the
wrong thing, since ":(glob)" behavior is already the default (it is
used only to countermand an earlier --noglob-pathspecs).
So we _could_ loosen the guard to allow :(glob), since it just
behaves the same as pathspecs do by default. But it seems like a
backwards step to do so. It already doesn't work (it hits the BUG()
case currently), and given that the user took an explicit step to
say "this pathspec should glob", it is reasonable for us to say "no,
--follow does not support globbing" (or in the case of log.follow,
avoid turning on follow mode). Which is what happens after this
patch.
- The set of allowed pathspec magic is obviously the same as in
GUARD_PATHSPEC(). We could perhaps factor these out to avoid
repetition. The point of having separate masks and GUARD calls is
that we don't necessarily know which parsed pathspecs will be used
where. But in this case, the two are heavily correlated. Still,
there may be some value in keeping them separate; it would make
anyone think twice about adding new magic to the list in
diff_check_follow_pathspec(). They'd need to touch
try_to_follow_renames() as well, which is the code that would
actually need to be updated to handle more exotic pathspecs.
- The documentation for log.follow says that it enables --follow
"...when a single <path> is given". We could possibly expand that to
say "with no unsupported pathspec magic", but that raises the
question of documenting which magic is supported. I think the
existing wording of "single <path>" sufficiently encompasses the
idea (the forbidden magic is stuff that might match multiple
entries), and the spirit remains the same.
Reported-by: Jim Pryor <dubiousjim@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
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