Detect git Directory with Bash

One interesting aspect of working at Mozilla is that Firefox lives in a mercurial repository while several other projects live on GitHub in a git repository. While most focus on either Firefox or another project, I switch between both, leaving me running git commands inside the mercurial repository and hg commands inside git repos. It's a frustration that I've lived with for a while so I sought to find a unified way of completing common tasks.

The first step was learning to detect git from command line:

if git rev-parse --git-dir > /dev/null 2>&1; then
  # git repo!
else
  # NOT a git repo!
fi

The if statement above detects a git repository, the else means the current directory is not inside a git repo.

One frequent task is checking out master and pulling the latest code from upstream, so I create an alias to do just that:

master() {
  if git rev-parse --git-dir > /dev/null 2>&1; then
    git checkout master && git pull upstream master
  else
    hg pull && hg checkout "last(public())"
  fi
}

This alias will save me time and frustration moving forward, and I'm sure I'll find other aliases to create based on git detection!