How to restrictively update submodules?

Question

I have a git project that I'd like to clone and update submodules on. I clone the project with

git clone --single-branch -b my_branch ssh://my_repo my_repo

I can init and pull submodules with

git submodule init
git submodule update

The problem I'm having is that all repository's git history (~ 1.3Gb) is being pulled with the update on each submodule. My .gitmodules file looks like

[submodule "mod_1"]
  path = path/to/mod_1
  url = my_repo
  branch = mod_1_branch
[submodule "mod_2"]
  path = path/to/mod_2
  url = my_repo
  branch = mod_2_branch

In the git clone command above I use --single-branch option which resolves the problem for the whole repository. As far as I know this option is not available for git submodule update.

How can I restrict submodules to pull only their branch history? Could there be an appropriate custom command (as described here under update > custom command)?

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

Unfortunately at the moment you cannot shallow fetch (git fetch --depth=1) a specified commit object.

However in Git 2.5+ (Q2 2015), fetching a single commit (without cloning the full repo) will be possible, through the new server-side config uploadpack.allowReachableSHA1InWant.

Its documentation says:

uploadpack.allowReachableSHA1InWant::

Allow upload-pack to accept a fetch request that asks for an
object that is reachable from any ref tip. However, note that
calculating object reachability is computationally expensive.
Defaults to false.

For more details see Pull a specific commit from a remote git repository.

How to restrictively update submodules?

1 Answers1