In Git, local branches can track one another - how is this useful?

Question

I heard that in Git, you can let a local branch A track another local branch B.

Why would someone want to do that?

Answer 1

The main things that come to mind for having a local branch track another local branch are (1) more informed messages from Git regarding a branch being ahead/behind of the tracked branch and (2) trigger hooks.

One area Git displays more information is when creating a branch. Creating a basic branch looks like the following:

$ git co -b A master Switched to a new branch 'A' 

While creating a tracking branch looks like:

$ git co --track -b B master Branch B set up to track local branch master. Switched to a new branch 'B' 

This would add the following in .git/config:

[branch "B"]     remote = .     merge = refs/heads/master 

After committing some changes on branches A and B, executing git status -s -b on branch A displays ## A while on branch B it displays ## B...master [ahead 1, behind 1], providing some quick information regarding the relationship between branches B and master.

The other area where you might want a local branch track another local branch is to trigger hooks; in particular pre-receive, update, post-receive and post-update during a git push. You might have hooks to, for example, trigger a build on a continuous integration server, do some license header checks, check for white space format errors, etc.