Use git show-ref to Check for Branch Existence

Today I learned how to check in git if a branch exists on my local repo. I bounce between projects that use a main or master branch and wanted to automate away checking which to use.

git show-ref lists references in a local git repository. It can show any ref, be it tag or branch or whatever. But we want to use it for branches:

# let's say this repo has `main` branch, not `master`
$ git show-ref --branches master
$ git show-ref --branches main
2067645fb4d7b6ab07215c025dee95b872150db2 refs/heads/main

Note it's important to filter by branches, otherwise you can get false positives from remotes or tags

$ git show-ref main
2067645fb4d7b6ab07215c025dee95b872150db2 refs/heads/main
2067645fb4d7b6ab07215c025dee95b872150db2 refs/remotes/origin/main

You can use the existence of output from this command in scripts to, for example, determine which branch to rebase against:

#!/bin/sh

main_exists=`git show-ref --branches main`
if [ -n "$main_exists" ]; then
  branch="main"
else
  branch="master"
fi;

git rebase -i $branch

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