# [BUG] rewriting history with filter-branch --commit-filter

3 messages from 2014-08-20 to 2014-08-20. Participants: Davide Fiorentino, Jeff King.
Thread: https://gitlist.dev/t/37383

## Davide Fiorentino, 2014-08-20 08:16

Subject: [BUG] rewriting history with filter-branch --commit-filter
Message-ID: <17DBA232-E993-4B3C-9952-90424976A28D@gmail.com>
URL: https://gitlist.dev/e/17DBA232-E993-4B3C-9952-90424976A28D%40gmail.com

```
Hi,

I was in the need to rewrite author name and email and commit date for a single commit and I guess I found a bug.
I run this git-filter script

$ git filter-branch --commit-filter ‘
    if [ "$GIT_COMMIT"="9cfca27" ]; 
        then GIT_AUTHOR_NAME=“Michelle”; 
            GIT_AUTHOR_EMAIL=“michelle@email.com”; 
            GIT_AUTHOR_DATE="2009-12-31T23:59:59”; 
            git commit-tree "$@“; 
        else 
            git commit-tree "$@“;
    fi' HEAD

and found that all history was rewritten as if “Michelle” not only commit 9cfca27.

I also tried using full length commit id and a non-existing commit id: nothing changes.
In the following example to replicate the replicate the bug I’m using a non-existing commit id to make the effect more evident.


$ git --version
git version 2.0.1

$ mkdir project

$ cd project

$ git init

$ for i in 1 2 3; do echo "foo" >> foo$i.txt; git add foo$i.txt; git commit -m "foo$i"; done
[master (root-commit) 89dec6e] foo1
 1 file changed, 1 insertion(+)
 create mode 100644 foo1.txt
[master 8a3c8e5] foo2
 1 file changed, 1 insertion(+)
 create mode 100644 foo2.txt
[master a3ca061] foo3
 1 file changed, 1 insertion(+)
 create mode 100644 foo3.txt

$ git log --graph --all --pretty=format:'%C(yellow)%h%C(cyan)%d%Creset %s %C(white)- %an, %ar%Creset'
* a3ca061 (HEAD, master) foo3 - David, 4 seconds ago
* 8a3c8e5 foo2 - David, 4 seconds ago
* 89dec6e foo1 - David, 4 seconds ago

$ git filter-branch --commit-filter '
    if [ "$GIT_COMMIT"="308add7" ]; 
        then GIT_AUTHOR_NAME="Michelle"; 
            GIT_AUTHOR_EMAIL="michelle@email.com"; 
            GIT_AUTHOR_DATE="2009-12-31T23:59:59"; 
            git commit-tree "$@"; 
        else 
            git commit-tree "$@";
    fi' HEAD

$ git log --graph --all --pretty=format:'%C(yellow)%h%C(cyan)%d%Creset %s %C(white)- %an, %ar%Creset'
* 8937dff (HEAD, master) foo3 - Michelle, 4 years, 8 months ago
* 30e494e foo2 - Michelle, 4 years, 8 months ago
* 2a2ba4f foo1 - Michelle, 4 years, 8 months ago
* a3ca061 (refs/original/refs/heads/master) foo3 - David, 8 seconds ago
* 8a3c8e5 foo2 - David, 8 seconds ago
* 89dec6e foo1 - David, 8 seconds ago

$ git log
commit 8937dff7e6a3f5545c2242e3fd5d33acbabe6df4
Author: Michelle <michelle@email.com>
Date:   Thu Dec 31 23:59:59 2009 +0100

    foo3

commit 30e494ef27f16c5456e66214ea46b780581dfb48
Author: Michelle <michelle@email.com>
Date:   Thu Dec 31 23:59:59 2009 +0100

    foo2

commit 2a2ba4fd6b9627e237a12b47570a3f020a202b55
Author: Michelle <michelle@email.com>
Date:   Thu Dec 31 23:59:59 2009 +0100

    foo1


using env-filter, I managed to rewrite the history with this:

$ git filter-branch --env-filter '
 
name="$GIT_AUTHOR_NAME"
email="$GIT_AUTHOR_EMAIL"
 
if [ "$GIT_COMMIT" = "89dec6e4bc1fb3cff694ea83f5ed900dad43449e" ]
then
    name="Michelle"
    email="Michelle@email.com"
fi

export GIT_AUTHOR_NAME=“$name"
export GIT_AUTHOR_EMAIL=“$email"
'

Hope this helped.

Davide
```

## Jeff King, 2014-08-20 08:52

Subject: Re: [BUG] rewriting history with filter-branch --commit-filter
Message-ID: <20140820085247.GB12999@peff.net>
URL: https://gitlist.dev/e/20140820085247.GB12999%40peff.net
In-Reply-To: <17DBA232-E993-4B3C-9952-90424976A28D@gmail.com>

```
On Wed, Aug 20, 2014 at 10:16:11AM +0200, Davide Fiorentino wrote:

> I was in the need to rewrite author name and email and commit date for a single commit and I guess I found a bug.
> I run this git-filter script
> 
> $ git filter-branch --commit-filter ‘
>     if [ "$GIT_COMMIT"="9cfca27" ]; 
>         then GIT_AUTHOR_NAME=“Michelle”; 
>             GIT_AUTHOR_EMAIL=“michelle@email.com”; 
>             GIT_AUTHOR_DATE="2009-12-31T23:59:59”; 
>             git commit-tree "$@“; 
>         else 
>             git commit-tree "$@“;
>     fi' HEAD
> 
> and found that all history was rewritten as if “Michelle” not only commit 9cfca27.

The filter snippets you provide to filter-branch are shell script. The
`[` command (aka `test`) is just another shell command, and follows the
usual whitespace splitting rules. In your command:

  [ "$GIT_COMMIT"="9cfca27" ]

it sees only one single argument, all concatenated together. A single
argument given to `test` is the same as `test -n`: it tells you whether
the string is empty, so this conditional is always true. You wanted:

  [ "$GIT_COMMIT" = "9cfca27" ]

instead. The whitespace makes the "=" a separate argument, and the
command knows it's an operator. You should also use the full commit id,
as that is what will be in $GIT_COMMIT.

-Peff

```

## Davide Fiorentino, 2014-08-20 08:59

Subject: Re: [BUG] rewriting history with filter-branch --commit-filter
Message-ID: <014F6E4D-96E8-451A-B7D4-379C260240FD@gmail.com>
URL: https://gitlist.dev/e/014F6E4D-96E8-451A-B7D4-379C260240FD%40gmail.com
In-Reply-To: <20140820085247.GB12999@peff.net>

```
Damn! I haven’t seen that missing space.

Thank you Peff!

Davide
```