commit: preserve commit hash on a no-op amend#2334
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A later change adds a second caller that commits the index lock and dies on failure, so wrap that into a helper to avoid duplicating its message. No functional change intended. Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
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"git commit --amend --no-edit" reset the committer date to "now" and rewrote the commit even when nothing else changed, moving the branch tip to a new hash for an effective no-op. Build the amended commit reusing the existing committer date: if that reproduces the current commit, leave the branch alone, report "nothing to amend", and skip the reflog entry and the post-commit and post-rewrite hooks. Signing always rewrites the commit, since its signature cannot reproduce the original, so it skips this detection. Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
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Submitted as pull.2334.git.git.1781342189.gitgitgadget@gmail.com To fetch this version into To fetch this version to local tag |
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Johannes Sixt wrote on the Git mailing list (how to reply to this email): Am 13.06.26 um 11:16 schrieb Harald Nordgren via GitGitGadget:
> git commit --amend --no-edit rewrote the commit and moved the branch tip
> even when nothing changed, because the committer date was reset to "now".
> Reuse the existing committer date so a no-op amend keeps the commit hash and
> leaves the branch untouched.
`git commit --amend --no-edit` is a way to set the committer timestamp
to the current time without changing other aspects of the commit. This
takes away this ability, doesn't it?
Is this keyed to --no-edit? Why is this mode special? Wouldn't it be an
identical case when the commit message is passed to the editor, but
comes back unchanged?
An invocation of `git commit` asks to "please make a new commit". But in
the suggested mode, no new commit is created. Shouldn't this then be
regarded as failure?
What happens with the current branch? Is it left unchanged (no ref
update occurs) or is it changed (a ref update occurs, but it happens to
be a no-op)? And does this then generate a reflog entry?
The updated documentation says about signed commits (note: I am totally
clueless about commit signing procedures):
> A commit that is being signed (`-S`, or `commit.gpgsign`)
> is always rewritten, since its signature cannot reproduce the original.
But if the commit doesn't change in any way, why should the signature be
invalidated, rewritten, or updated?
-- Hannes
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git commit --amend --no-editrewrote the commit and moved the branchtip even when nothing changed, because the committer date was reset to
"now". Reuse the existing committer date so a no-op amend keeps the
commit hash and leaves the branch untouched.
A real change (tree, message, author, committer, or signing) still
rewrites as before.
cc: Johannes Sixt j6t@kdbg.org