RE: [PATCH] diff: respect --no-ext-diff with typechange
From: Jakub Vrana <hidden>
Date: 2016-06-15 22:54:16
Yes, I was fixing the invalid (!pgm) condition, sorry for a non-precise description. Does it mean that my patch is accepted or is there something else I need to do? -- Jakub Vrana -----Original Message----- From: Jeff King [mailto:peff@peff.net] Sent: Monday, July 16, 2012 9:16 PM To: Jakub Vrana Cc: git@vger.kernel.org; gitster@pobox.com Subject: Re: [PATCH] diff: respect --no-ext-diff with typechange On Mon, Jul 16, 2012 at 05:27:00PM -0700, Jakub Vrana wrote:
If external diff is specified through diff.external then it is used even if `git diff --no-ext-diff` is used when there is a typechange.
Eek. That has some minor security implications, as it means that it is dangerous to run even plumbing inspection command in somebody else's repository. However...
quoted hunk ↗ jump to hunk
diff.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/diff.c b/diff.c index 208096f..898d610 100644 --- a/diff.c +++ b/diff.c@@ -3074,6 +3074,9 @@ static void run_diff(struct diff_filepair *p,struct diff_options *o) if (o->prefix_length) strip_prefix(o->prefix_length, &name, &other); + if (!DIFF_OPT_TST(o, ALLOW_EXTERNAL)) + pgm = NULL; + if (DIFF_PAIR_UNMERGED(p)) { run_diff_cmd(pgm, name, NULL, attr_path, NULL, NULL, NULL, o, p);
run_diff_cmd already checks the ALLOW_EXTERNAL bit and sets pgm to NULL there. So as far as I can tell, we are not actually running the external diff. However, there is still a problem. Later in run_diff we do:
if (!pgm &&
DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two) &&
(S_IFMT & one->mode) != (S_IFMT & two->mode)) {
/*
* a filepair that changes between file and symlink
* needs to be split into deletion and creation.
*/
struct diff_filespec *null = alloc_filespec(two->path);
run_diff_cmd(NULL, name, other, attr_path,
one, null, &msg, o, p);
free(null);
strbuf_release(&msg);
null = alloc_filespec(one->path);
run_diff_cmd(NULL, name, other, attr_path,
null, two, &msg, o, p);
free(null);
}
else
run_diff_cmd(pgm, name, other, attr_path,
one, two, &msg, o, p);
IOW, we split up a typechange if we are feeding it to the internal diff generator, because builtin_diff will not show diffs between different types. But the check for "!pgm" here is not right; we don't know yet whether we will be builtin or external, because we have not checked ALLOW_EXTERNAL yet.
So I think your fix is the right thing, but the bug it is fixing is not "do not run external diff even when --no-ext-diff is specified". It is "do not accidentally feed typechange diffs to builtin_diff".
You can see the difference in output with this script (and it works fine with your patch applied):
git init -q repo && cd repo &&
echo content >file && git add file && git commit -q -m regular &&
rm file && ln -s dest file && git commit -q -a -m typechange &&
export GIT_PAGER=cat &&
export GIT_EXTERNAL_DIFF='echo doing external diff' &&
git show HEAD^ --format='=== %s, ext ===' --ext-diff &&
git show HEAD^ --format='=== %s, no-ext ===' --no-ext-diff &&
git show HEAD --format='=== %s, ext ===' --ext-diff &&
git show HEAD --format='=== %s, no-ext ===' --no-ext-diff
-Peff