showing git branch name in command prompt

Question

Just curious if the following two always output the same thing (branch name)? I'm using zsh.

git rev-parse --abbrev-ref HEAD 2> /dev/null

versus

ref=$($git symbolic-ref HEAD 2> /dev/null)
echo "${ref#refs/heads/}"

If not, is one way preferred over the other for setting up git context in command prompt?

Answer 1

They behave the same when on a branch, but not when in "detached HEAD" mode (try git checkout --detach master for instance, followed by git checkout master to re-attach your head).

The real question to answer is: what do you want displayed in detached HEAD mode? If you want an abbreviated hash, use the rev-parse format. If you want something else, use the symbolic-ref format, perhaps with an additional clause to show "detached" or whatever, if symbolic-ref errors out.

Answer 2

@torec posted an excellent explanation of the differences between the 2, i just want to take it a bit further and to explain a bit more about the syntx of each command.

---

git rev-parse --abbrev-ref HEAD 2> /dev/null

---

rev-parse

--abbrev-ref[=(strict|loose)]
A non-ambiguous short name of the objects name.
The option core.warnAmbiguousRefs is used to select the strict abbreviation mode.

HEAD

Read here all about HEAD (+detached HEAD) here

So what this command does it simply get the SHA-1 of HEAD (rev-parse), and them converts it tote branch name (--abbrev-ref)

---

git symbolic-ref HEAD

symbolic-ref Given one argument, reads which branch head the given symbolic ref refers to and outputs its path, relative to the .git/ directory.

Typically you would give HEAD as the argument to see which branch your working tree is on

The ( symbolic-ref ) is usually used if you wish to do something regrading refs (or refspec(