Thomas RastRather counterintuitively,
$ git rev-parse --verify aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
does *not* fail. The check is based solely on whether we can come up with something that "looks like" a SHA1, not whether the object actually exists. To wit:
# this cannot be done with update-ref as that *does* check $ echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa > .git/refs/heads/nonexistent $ git rev-parse --verify nonexistent aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
Note that the commit message of 79162bb makes clear that this is exactly the intended behaviour:
git-rev-parse: Allow a "zeroth" parent of a commit - the commit itself.
This sounds nonsensical, but it's useful to make sure that the result is a commit. [...] Also, since the "parent" code will actually parse the commit, this, together with the "--verify" flag, will verify not only that the result is a single SHA1, but will also have verified that it's a proper commit that we can see.
Document this clearly in the description for --verify.
Furthermore the second item in EXAMPLES
* Print the commit object name from the revision in the $REV shell variable:
seems to imply that rev-parse should actually check that the object exists *and* is a commit, when in reality it does neither. We could suggest the ^0 trick alluded to above, but instead document the more verbose (and clear)
$ git rev-parse --verify "$REV^{commit}"Observe that if you ran
$ git rev-parse --verify "nonexistent^{commit}"after the above setup, the failure would come from the ^{} peeling operator and not from --verify.
Noticed-by: Zachery Hostens <zacheryph@gmail.com> Signed-off-by: Thomas Rast <trast@student.ethz.ch> --- Documentation/git-rev-parse.txt | 23 +++++++++++++++++------ 1 files changed, 17 insertions(+), 6 deletions(-)
Show changes to Documentation/git-rev-parse.txt +17 −6
diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt index ff23cb0..779fa87 100644 --- a/Documentation/git-rev-parse.txt +++ b/Documentation/git-rev-parse.txt @@ -59,8 +59,9 @@ OPTIONS instead. --verify:: - The parameter given must be usable as a single, valid - object name. Otherwise barf and abort. + The parameter must either be formed like an object name, or + dereference to an object name. This does 'not' verify that + the object actually exists! See EXAMPLES below. -q:: --quiet:: @@ -292,21 +293,31 @@ EXAMPLES $ git rev-parse --verify HEAD ------------ -* Print the commit object name from the revision in the $REV shell variable: +* Print the object name from the revision in the $REV shell variable: + ------------ $ git rev-parse --verify $REV ------------ + -This will error out if $REV is empty or not a valid revision. +This will error out if $REV does not dereference to a well-formed +object name (i.e., SHA1). -* Same as above: +* Same as above, but also verify that the object exists and is a commit: ++ +------------ +$ git rev-parse --verify "$REV^{commit}" +------------ ++ +This works because the `{caret}\{commit\}` peeling operator will fail +unless the object exists and can be peeled into a commit. + +* Print the object name from $REV, but default to master: + ------------ $ git rev-parse --default master --verify $REV ------------ + -but if $REV is empty, the commit object name from master will be printed. +If $REV is empty, the commit object name from master will be printed. Author
-- 1.7.4.rc1.309.g58aa0
