How can I populate the Git commit ID into a file when I commit?

Question

I would like to create Git hook(s) that will populate the commit id of the commit I am about to make into a file (basically variable substitution) in my source code. Is this

Answer 1

It's impossible to do what you want: the commit's SHA-1 hash is calculated over the whole repository snapshot including each member file, so there's the chicken and egg problem — to calculate the commit's hash you need to know the contents of all the files which comprise it.

Answer 2

I was looking for an answer to this question. The Commit Id is already written to a file you just have to know where to look. After making a commit on the master branch, you can find the commit hash at ./.git/refs/heads/master So in our continuous delivery solution (it downloads the .git folder along with the source code) we can simply cat ./.git/refs/heads/${BRANCH} in order to associate the current commit hash with our build

Answer 3

The key here is to put your revision ID into some file that Git doesn't care about. Here is a fragment from one of my projects:

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AssemblyCS="Properties/AssemblyInfo.cs"
rev="$(git log -n 1 --date=short --format=format:"rev.%ad.%h" HEAD)"
sed  "$AssemblyCS"
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This script is run as part of my build process (it could also be a post-commit hook). In this case Properties/AssemblyInfo.cs is in .gitignore whereas Properties/AssemblyInfo.cs.in is under version control. The build uses the .csfilewhich includes a revision ID that ends up in the deployed executable.