Edit log message after commit

Hi,

Is there any method to edit the log message after committed? I couldn't find any information in Documentation and in git mailing list.

Regards, Kevin Leung

Kevin Leung <hysoka@gmail.com> writes:

Undoing and re-committing can be done with the following recipe.

There is a *big* *red* *warning*, though. If you have already made available the commit you are about to undo to others, and later other people have made more commits on top of them, merging their changes back to your repository would make the commit history look a bit funny. You could still do this without damaging the repository. This warning only applies to the shape of the commit graph.

First, the easiest case. Undoing and recommitting the latest commit in the current branch.

(1) Run "git diff HEAD" and make sure that your working tree
    matches the latest commit you are about to undo.  Then:

    $ git reset --soft HEAD^

    This leaves the working tree intact (i.e. it still has what
    you to have in the commit you are "fixing").

(2) Optional.  If you wanted to make changes other than commit
    log, do your edit here in the working tree.  When done, run
    "git diff HEAD" to make sure the changes are what you want
    the "fixed" commit to have.

(3) Run:

    $ git commit -c ORIG_HEAD

    If you made changes in (2) and have not done
    "git-update-index" on them, you may want to add '-a' there.
    If you are just redoing the log message you probably would
    not.

    This gives you the editor with the log message from the
    commit you undone in step (1).  Do your edit and exit the
    editor as usual.

Look at the output in "gitk HEAD ORIG_HEAD" to understand what happened. You just rewound a commit, and made a different commit.

Harder, more cumbersome case, is when you realize that you made a mistake a several commits ago. This is described in detail in Documentation/howto/revert-branch-rebase. Read it.

No. Once a git object is created it is immutable (since its name is the hash of its contents). If you realise right after you make a commit that you want to change the message, you would have to redo it ... use git diff or git whatchanged to get the details and the diffs, then use git reset to backup, and re-apply.

If you have made subsequent commits, then you'll have to back those out and redo them too.

If you have published your tree, then it's better to live with the 'bad' commit than try to re-write history.

-Tony

Kevin Leung wrote:

The commit must be at the head, or else you can't change it without breaking the chain of following commits. If you are using Cogito, use cg-admin-uncommit and then re-commit it. Otherwise, create a new commit object for the same tree and parent(s) as the old commit, with the new message. The new commit object is your new head.

--
				Brian Gerst

Thank you all of you. I was able to redo the commit.

But as Tony has pointed out. I would have needed to redo all the subsequent commits if I was to change non-HEAD commit message. What is the proper way of doing that? Is it the same as Documentation/howto/revert-branch-rebase.txt ?

One more question is that, how to use the git commit --reedit-message flag? According to Documentation/howto/rebase-and-edit.txt, I guess the meaning is to re-apply one commit to current HEAD?

At Thu, 29 Sep 2005 15:45:49 +0800, Kevin Leung wrote:

as pointed out by others, if the tree is already public, do revert. otherwise, use git-cherry-pick and git-rebase might help. but it might not be a good idea. (don't know)

to illustrate this, create the following tree

c
|
b
|
a
|
initial

    git-init-db
    echo hello > hello.c
    git-update-index --add hello.c
    git-commit -v -m 'initial'
    echo a >> hello.c
    git-commit -a -m 'add a'
    echo b >> hello.c
    git-commit -a -m 'add b'
    echo c >> hello.c
    git-commit -a -m 'add c'

say, you want to edit the commit message for 'add a'.

first, create new branch at where you wanna change the message

    git checkout -b temp HEAD^^^   # hmm... HEAD^3 doesn't work

cherry pick the 'add a' commit but don't commit yet

    git-cherry-pick -n master^^

commit the change with reediting the original commit log

    git commit --reedit master^^

rebase the _master_ to temp

    git-checkout master
    git-rebase temp

I'm pretty sure that there is better way to do it and these should be easy to be scripted.

my two cents,
--
          yashi

Yasushi SHOJI <yashi@atmark-techno.com> writes:

Because it should be spelled HEAD~3. HEAD^3 is "the third parent of HEAD" and usually does not exist, unless you are talking about an Octopus merge of three or more branches.

Kevin Leung <hysoka@gmail.com> wrote:

As the others said, a commit object is immutable but it can be replaced with a new one and the path from HEAD changed. If you need to do this often, have a look at StGIT. It allows you to create patches as git commit objects and indefinitely edit them (both file changes and commit information like log messages, author etc.).

In the latest snapshot, I also added a commit command to permanently store the patches into the repository after which you won't be able to edit them anymore (that's useful for maintainers using StGIT, not only contributors).

Thanks Yashi and Catalin for the pointers. The information is exactly what I was looking for. :-)