How can I specify a branch/tag when adding a Git submodule?

user_16957 0
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How does git submodule add -b work?

After adding a submodule with a specific branch, a new cloned repository (after git submodule update --init) will be at a specific commit, not the branch itself (git status on the submodule shows "Not currently on any branch").

I can't find any information on .gitmodules or .git/config about the submodule's branch or any specific commit, so how does Git figure it out?

Also, is it possible to specify a tag instead of a branch?

I'm using version 1.6.5.2.

git-submodules git
13 Answers

In my experience switching branches in the superproject or future checkouts will still cause detached HEADs of submodules regardless if the submodule is properly added and tracked (i.e. @djacobs7 and @Johnny Z answers).

And instead of manually checking out the correct branch manually or through a script git submodule foreach can be used.

This will check the submodule config file for the branch property and checkout the set branch.

git submodule foreach -q --recursive 'branch="$(git config -f $toplevel.gitmodules submodule.$name.branch)"; git checkout $branch'

user_11014710

Existing answers have the second step missing and overloaded with details.

To switch an existing submodule to track a new remote url and/or a new branch:

  1. Edit the source of truth in .gitmodules.

For example, from

[submodule "api"]
    path = api
    url = https://github.com/<original_repo>/api.git

to

[submodule "api"]
    path = api
    url = https://github.com/<another_repo>/api.git
    branch = work-in-progress

  1. git submodule sync: Updates the description of submodules cached by git in .git/modules from the just-edited source of truth specified in .gitmodules.

  2. git submodule update --init --recursive --remote: Updates the checked-out submodules in the working copy.

  3. Commit the changes.

user_5252030

The only effect of choosing a branch for a submodule is that, whenever you pass the --remote option in the git submodule update command line, Git will check out in detached HEAD mode (if the default --checkout behavior is selected) the latest commit of that selected remote branch.

You must be particularly careful when using this remote branch tracking feature for Git submodules if you work with shallow clones of submodules. The branch you choose for this purpose in submodule settings IS NOT the one that will be cloned during git submodule update --remote. If you pass also the --depth parameter and you do not instruct Git about which branch you want to clone -- and actually you cannot in the git submodule update command line!! -- , it will implicitly behave like explained in the git-clone(1) documentation for git clone --single-branch when the explicit --branch parameter is missing, and therefore it will clone the primary branch only.

With no surprise, after the clone stage performed by the git submodule update command, it will finally try to check out the latest commit for the remote branch you previously set up for the submodule, and, if this is not the primary one, it is not part of your local shallow clone, and therefore it will fail with

fatal: Needed a single revision

Unable to find current origin/NotThePrimaryBranch revision in submodule path 'mySubmodule'

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