Subject: Re: changing log entries

From: Andy Parkins <[email-masked]>
Date: Thu, 14 Dec 2006 10:37:34 +0000

On Wednesday 2006 December 13 23:08, Jon Masters wrote:

> Anyway, now I would like to change an existing log entry to make it a
> bit cleaner (read: add a first line that's under 80 characters). What's
> the best way to change an existing log entry for a commit?

If it's HEAD you want to change:
 git-commit --amend

If it's not, it's a bit harder.  You could pull each commit out as a patch and 
apply them again later after a git-reset.  However, git has a tool for 
automating a lot of that:  git-rebase.  man git-rebase has some excellent 
examples.

 * -- A -- B -- C (master)

Let's say you want to edit A; make a new branch at A:

$ git branch temp-edit-branch master^^
 
 * -- A (temp-edit-branch)
       \
        B -- C (master)

Edit A with git-commit --amend.  This makes a new A, A' that has the new 
commit message:

 * -- A' (temp-edit-branch)
  \
   A -- B -- C (master)

Then you switch to "master" and rebase master onto temp-edit-branch; you can 
then delete temp-edit-branch

$ git-checkout master
$ git-rebase temp-edit-branch
$ git branch -D temp-edit-branch

 * -- A' -- B' -- C' (master)
  \
   A -- B -- C

Note that A-B-C are now dangling commits; a git-prune would be needed to clean 
them out of the repository.

The important thing to realise is that you can never really edit a commit.  
The best you can do is reapply it.  In this example, the fact that B' makes 
the same change as B is irrelevant - they are two separate commits.

Note: this is only workable if you haven't pushed this branch to another 
repository.  The other repository would retain the original A--B--C branch 
and you will get "won't fast forward" errors if you try to push the 
new "A'--B'--C'" branch.

Andy
-- 
Dr Andy Parkins, M Eng (hons), MIEE