Question

I have a git repository with multiple branches. The repository has a makefile which is identical between branches. I’d like to create a bash script that can be run on a regular basis that pulls all branches from the remote repository and then runs make for every branch that has changed, or been added. The executable created is then moved to another location on the server, and a make clean would be run before beginning on the next branch to be processed.

The order of commands I’d be running would be

make
cp executable /some/other/directory/branch_name
make clean

Is this even possible to do with a shell script, if it is how could I go about implementing this. If a shell script is ill suited to this task, how else can I go about achieving the same result?

Answer 1

I’d do something like this:

# fetch updates, but don't merge yet
git fetch    # origin is default

# list all branches
git for-each-ref --format='%(refname:short)' refs/heads |
while read branch; do
    # if the branch is not the same as the remote branch...
    if [ "$(git rev-parse $branch)" != "$(git rev-parse origin/$branch)" ]; then
         # only continue to the next step on successful results
         git checkout $branch &&
         git pull &&
         (make &&
         cp executable /somewhere/else;
         make clean)
         # except always make clean as long as we tried to make
         #
         # you might also consider a hard reset and clean, to guarantee things
         # are safe for the next checkout
    fi
done

The nice thing about fetching first is that you don’t have to unnecessarily check out branches with no changes; if your repo is big this can be a time-saver.

Obviously there are choices to be made about handling errors; I just went with the simplest thing that still made sense. For more complex handling, you might instead want to do things of the form if make; then ...; else ...; fi, e.g.:

# die hard on unexpected checkout/pull failures
if ! (git checkout $branch && git pull); then
    exit 1
fi
if make; then
    cp executable /somewhere/else
else
    # report a build failure?
fi
# clean up no matter what
git clean -xdf
git reset --hard