# git-diff across branches?

3 messages from 2008-01-08 to 2008-01-08. Participants: Gonzalo Garramuño, Jeff King, Jakub Narebski.
Thread: https://gitlist.dev/t/11522

## Gonzalo Garramuño, 2008-01-08 08:44

Subject: git-diff across branches?
Message-ID: <478337DE.7@advancedsl.com.ar>
URL: https://gitlist.dev/e/478337DE.7%40advancedsl.com.ar

```

I was wondering if there was a way to make a git-diff across (local) 
branches.

Something like:

$ git-diff --branch test1 HEAD --branch test2 HEAD  file.cpp
(would show a diff for file.cpp between test1 HEAD and test2 HEAD)



-- 
Gonzalo Garramuño
ggarra@advancedsl.com.ar

AMD4400 - ASUS48N-E
GeForce7300GT
Xubuntu Gutsy

```

## Jeff King, 2008-01-08 08:57

Subject: Re: git-diff across branches?
Message-ID: <20080108085705.GA4222@sigill.intra.peff.net>
URL: https://gitlist.dev/e/20080108085705.GA4222%40sigill.intra.peff.net
In-Reply-To: <478337DE.7@advancedsl.com.ar>

```
On Tue, Jan 08, 2008 at 05:44:14AM -0300, Gonzalo Garramuño wrote:

> I was wondering if there was a way to make a git-diff across (local)  
> branches.
>
> Something like:
>
> $ git-diff --branch test1 HEAD --branch test2 HEAD  file.cpp
> (would show a diff for file.cpp between test1 HEAD and test2 HEAD)

I think you are mistaken about how HEAD works; it is a pointer to a
particular branch. So there is no "HEAD" for test1; there is simply
test1, and from time to time your repository's HEAD points to test1.

However, that makes things easier. You can simply do this:

  git-diff test1 test2 file.cpp

Unless you mean that you have two separate repositories, test1 and
test2. In which case each _does_ have its own HEAD, and you will have to
fetch from one repo into the other to get your answer:

  # go into one of the repos
  cd test1
  # fetch the 'master' ref from the other repo and store it in this repo
  # using the name 'test2'
  git fetch ../test2 master:test2
  # now we can diff between them
  git diff HEAD test2 file.cpp

-Peff

```

## Jakub Narebski, 2008-01-08 10:01

Subject: Re: git-diff across branches?
Message-ID: <m3wsqkmy22.fsf@roke.D-201>
URL: https://gitlist.dev/e/m3wsqkmy22.fsf%40roke.D-201
In-Reply-To: <20080108085705.GA4222@sigill.intra.peff.net>

```
Jeff King <peff@peff.net> writes:

> On Tue, Jan 08, 2008 at 05:44:14AM -0300, Gonzalo Garramuño wrote:
> 
> > I was wondering if there was a way to make a git-diff across (local)  
> > branches.
> >
> > Something like:
> >
> > $ git-diff --branch test1 HEAD --branch test2 HEAD  file.cpp
> > (would show a diff for file.cpp between test1 HEAD and test2 HEAD)
> 
> I think you are mistaken about how HEAD works; it is a pointer to a
> particular branch. So there is no "HEAD" for test1; there is simply
> test1, and from time to time your repository's HEAD points to test1.
> 
> However, that makes things easier. You can simply do this:
> 
>   git-diff test1 test2 file.cpp

Canonically it is

  # git diff test1 test2 -- file.cpp

but you can also use (for example if file was renamed)

  # git diff test1:file.cpp test2:file.cpp
 
> Unless you mean that you have two separate repositories, test1 and
> test2. In which case each _does_ have its own HEAD, and you will have to
> fetch from one repo into the other to get your answer:
[cut]

Not necessary. If those two repositories are on the same local
filesystem, you can use trick from GitTips:

  http://git.or.cz/gitwiki/GitTips#head-9f79516c05f0c1b51945b848adb3dd1c5a2bf016

  (assuming we are in test1, and ../test2 is relative path to test2)
  # GIT_ALTERNATE_OBJECT_DIRECTORIES=../test2/.git/objects git diff-tree \
     $(GIT_DIR=../test2/.git git rev-parse --verify HEAD) HEAD

-- 
Jakub Narebski
Poland
ShadeHawk on #git

```