# Re: using rev-list to tell if a branch is behind or ahead

1 messages from 2008-05-20 to 2008-05-20. Participants: Tim Harper.
Thread: https://gitlist.dev/t/13591

## Tim Harper, 2008-05-20 20:33

Subject: Re: using rev-list to tell if a branch is behind or ahead
Message-ID: <19466E30-0877-4AE9-BA1D-A8A32C8989C5@gmail.com>
URL: https://gitlist.dev/e/19466E30-0877-4AE9-BA1D-A8A32C8989C5%40gmail.com
In-Reply-To: <F3CD27F7-D509-41A3-B3C8-0B9124537DDA@gmail.com>

```
On May 20, 2008, at 2:24 PM, Shawn O. Pearce wrote:
> Tim Harper <timcharper@gmail.com> wrote:
>> I'm implementing a ruby interface to git and am wanting to be able to
>> ask if a branch is ahead or behind.
>>
>> I looked in the builtin-checkout.c file and see this code:
>>
>> /* Run "rev-list --left-right ours...theirs" internally... */
> ...
>> It looks like it's calling rev-parse.  But, when I call it with the
>> same arguments (using branches or commit sha1's), it only will list
>> commits that are in right and not in left.  I need it to show both
>> ways: commits that are in the right and not in left, and commits that
>> are in the left but not in right.
>>
>> Do I need to call rev-parse twice to achieve this?
>
> No.  You need to use the triple dot operator ("...") not the
> double dot operator ("..").
>

Ugh... figured it was something simple.  Funny thing is, when I was  
looking at the c code:
strcpy(symmetric, sha1_to_hex(ours->object.sha1));
strcpy(symmetric + 40, "...");
strcpy(symmetric + 43, sha1_to_hex(theirs->object.sha1));

I was like "I wonder why the 3rd line is +43, and not +42".



>> Here's a sample of what I'm trying currently:
>> ~ $ mkdir test
>> ~ $ cd test/
>> ~/test $ git init
>> Initialized empty Git repository in .git/
>> ~/test $ git
>> ~/test $ echo content > file.txt
>> ~/test $ git add file.txt && git commit -m "Initial commit"
>> Created initial commit f5e4160: Initial commit
>> 1 files changed, 1 insertions(+), 0 deletions(-)
>> create mode 100644 file.txt
>> ~/test master$ git co -b task
>> Switched to a new branch "task"
>> ~/test task$ echo changes >> file.txt
>> ~/test task$ git add file.txt && git commit -m "Some changes"
>> Created commit 96492ee: Some changes
>> 1 files changed, 1 insertions(+), 0 deletions(-)
>> ~/test task$ git rev-list --left-right task..master --
>
> You need an extra "." between task and master, this should be:
>
> git rev-list --left-right task...master --
>
>> ~/test task$ git rev-list --left-right master..task --
>>> 96492ee80143f43417b00699ff29330d0027df7f
>
> -- 
> Shawn.

That did it, thanks

Tim

```