blob: e1021865e348b7757e0fd0e7148781068fd8ba98 [file] [log] [blame]
= commit-msg Hook
commit-msg - Edit commit messages to insert a `Change-Id` tag.
A Git hook automatically invoked by `git commit`, and most other
commit creation tools such as `git citool` or `git gui`. The Gerrit
Code Review supplied implementation of this hook is a short shell
script which automatically inserts a globally unique `Change-Id` tag
in the footer of a commit message. When present, Gerrit uses this
tag to track commits across cherry-picks and rebases.
After the hook has been installed in the user's local Git repository
for a project, the hook will modify a commit message such as:
Improve foo widget by attaching a bar.
We want a bar, because it improves the foo by providing more
wizbangery to the dowhatimeanery.
Signed-off-by: A. U. Thor <>
by inserting a new `Change-Id: ` line in the footer:
Improve foo widget by attaching a bar.
We want a bar, because it improves the foo by providing more
wizbangery to the dowhatimeanery.
Change-Id: Ic8aaa0728a43936cd4c6e1ed590e01ba8f0fbf5b
Signed-off-by: A. U. Thor <>
The hook implementation is reasonably intelligent at inserting the
`Change-Id` line before any `Signed-off-by` or `Acked-by` lines placed
at the end of the commit message by the author, but if no such
lines are present then it will just insert a blank line, and add
the `Change-Id` at the bottom of the message.
If a `Change-Id` line is already present in the message footer, the
script will do nothing, leaving the existing `Change-Id` unmodified.
This permits amending an existing commit, or allows the user to
insert the Change-Id manually after copying it from an existing
change viewed on the web.
The `Change-Id` will not be added if `gerrit.createChangeId` is set
to `false` in the git config.
To obtain the `commit-msg` script use `scp`, `wget` or `curl` to download
it to your local system from your Gerrit server.
You can use either of the below commands:
$ scp -p -P 29418 <your username>@<your Gerrit review server>:hooks/commit-msg <local path to your git>/.git/hooks/
$ curl -Lo <local path to your git>/.git/hooks/commit-msg <your Gerrit http URL>/tools/hooks/commit-msg
A specific example of this might look something like this:
$ scp -p -P 29418 ~/duhproject/.git/hooks/
$ curl -Lo ~/duhproject/.git/hooks/commit-msg
Make sure the hook file is executable:
$ chmod u+x ~/duhproject/.git/hooks/commit-msg
* link:user-changeid.html[Change-Id Lines]
* link:[git-commit(1)]
* link:[githooks(5)]
The hook generates unique `Change-Id` lines by creating a virtual
commit object within the local Git repository, and obtaining the
SHA-1 hash from it. Like any other Git commit, the following
properties are included in the computation:
* SHA-1 of the tree being committed
* SHA-1 of the parent commit
* Name, email address, timestamp of the author
* Name, email address, timestamp of the committer
* Proposed commit message (before `Change-Id` was inserted)
Because the names of the tree and parent commit, as well as the
committer timestamp are included in the hash computation, the output
`Change-Id` is sufficiently unique.
Part of link:index.html[Gerrit Code Review]