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

["Shawn O. Pearce" <spearce@spearce.org>]

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 ("..").

> 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.