Find commit of currently included subtree?

Hi all,

I have a subtree (from repo "Tools") included in our Git repo ("App") using "git subtree ...". This is all working fine.

The next step is to automate checking whether that subtree (in "App") needs to be updated. Checking the remote "Tools" repo for its latest commit is easy with "git ls-remote" but I did not find an (obvious) way to check what subtree is currently part of our repo ("App").

It looks like I could parse the message of the commit where the subtree was last updated. It contains a line like "git-subtree-split: 1234..cdef" that appears to match the included commit in "Tools". That seems rather fragile and relatively complex.

Or I could just run "git subtree" and parse its output (as it seems to notice if there is nothing to do)?

Any suggestions for a better/simpler way?

Cheers, Hilco