Best way for automated script to determine whether git is really installed on OS X

Question

I can locate executables named git in several ways (basically equivalent to which git). But all of the solutions I know about are defeated by OS X's fake /usr/bin/git program, which is a hook to a dialog offering to install Xcode's git (I'll refer to it subsequently as the OS X git installer.)

I want to detect that situation and treat git as not found if that is the only one. I don't want to have to execute it to determine that, because I don't want to trigger the installer dialog.

Context: I'd like to implement the following (as part of a larger software installation process):

• Determine whether a "real" git is installed (i.e., an executable named git, other than the OS X git installer, is on the PATH),
• If it is, recognize and respect it and proceed (I have this part figured out),
• If it is not, install the one from the git project (I have this part figured out).

I am comfortable parsing PATH if needed and searching for executables myself, if I can find a way to ignore the OS X git installer. I am comfortable with a heuristic if it gets this right almost all the time; I don't need to handle edge cases (like someone creating an executable or script called git that is not git-compatible).

What's the best (most robust, secondarily most convenient) way to determine whether a non-OS X git installer git is installed on a system without executing /usr/bin/git (and triggering the installer dialog)?

Answer 1

Alright, I think I have my answer, of the heuristic variety.

IF: /Applications/Xcode.app/ does not exist,

AND: /Library/Developer/CommandLineTools/ does not exist,

THEN: /usr/bin/git is the stub, and it can be ignored.

Obviously there are failure cases possible; people can move those files around, people can create executables named git that are not git-compatible, but this seems to be the 99% solution and turns out to be a little easier than I thought.

I haven't yet investigated what will happen if I install the git project's git, and what will happen in the PATH (will the Apple non-tool still be first?). If that changes anything substantial I'll report back; I am guessing if Apple's tool is still first in the PATH, I'll have my installation process move or delete it, or possibly change the PATH it uses, or something.

Answer 2

There is no best way. There are some things that defy automated discovery and I can certainly have $HOME/bin/git which isn't git but is in my path.

What you can do is make the path to git as a configurable item with a reasonable default and document it well. The git program itself does this itself; it will look for configuration items in a few different places and finally allows git --file configfile as a last option to override.