Re: git filter-branch re-write history over a range of commits did notwork

From: Johannes Sixt <j6t@kdbg.org>
Date: May 28, 2019, 06:23 UTC
Message-ID: <fa23e865-94ed-308f-6a19-75b6ea89eec3@kdbg.org>
In-Reply-To: <DB7PR05MB5573B5B80C8A9CBE867803D88D1E0@DB7PR05MB5573.eurprd05.prod.outlook.com>

Am 28.05.19 um 07:42 schrieb LU Chuck:

Show 16 quoted lines

>> From: Philip Oakley <philipoakley@iee.org>
>> The three dots is provided in the literal EXAMPLES section of the man page. That is
>> probably an error, as I think it is meant to be an ellipsis to indicate 'insert other
>> options here'.
>>
>> Simply remove the three dots ('symmetric diff notation') .
>>
>> Not sure what the correct change to the man page should be, but clearly it has
>> caused confusion. It also takes a moment to properly realise which commits the
>> two dot notation will refer to in the example which may further compound the
>> confusion about the three dots.
>>
>> Philip
> [LU Chuck] Hi Hannes,
>          I used ... literally when I cited the command. I write the command with ... directly as the document introduce the usage like that.
>          You can check the document https://git-scm.com/docs/git-filter-branch#_examples about the --env-filter section.

Copying and pasting examples literally is dangerous. You should know what you are doing.

"..." is a revision range that computes the mergebase between HEAD and HEAD, which is (surprise!) HEAD, and then includes the two end points, but excludes everything below the mergebase. So, the revision specification that your command ends up with is

     HEAD HEAD ^HEAD ^67d9d9 f70bf4

Which is empty if f70bf4 is an ancestor of HEAD.

>          Hi Philip,
>          I also tried to execute the command without ..., 
>          git filter-branch --env-filter 'export GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"' 67d9d9..f70bf4
>          then I will get another error " You must specify a ref to rewrite."

You cannot restrict your filter to a subset of commits like this. After all, all commits that descend from one of the rewritten commits must also change, up to and including to the branch refs. Therefore, it is necessary to mention the branches that you rewrite in this manner.

Perhaps:

   git filter-branch --env-filter '
     if git merge-base --is-ancestor $GIT_COMMIT f70bf4; then
       export GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"
     fi' -- 67d9d9..master

This assumes that only branch master is affected by the rewriting. Use --all if you have many affected branches.

-- Hannes