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Git submodules

This repository embeds https://github.com/dasch-swiss/0123-import-scripts as a Git submodule in src/dsp_tools/import_scripts. That means that src/dsp_tools/import_scripts has no contents, but only a reference to a certain commit in the main branch of 0123-import-scripts. When you clone DSP-TOOLS from GitHub as usual, src/dsp_tools/import_scripts will be empty.

Rationale to use a git submodule

The code of the 0123-import-scripts repository is closely related to the documentation of the excel2xml module. When something changes in excel2xml, the changes need not only be reflected in the docs, but also in 0123-import-scripts. This can easily be forgotten. The decision to embed it as a submodule is meant to bring 0123-import-scripts closer to the attention of the developers of DSP-TOOLS. For example, a repo-wide search for a string or the usage of a method will also yield results from 0123-import-scripts.

The example project rosetta is a similar case. Changes in DSP-TOOLS sometimes need to be reflected in rosetta. But since rosetta is not embedded as submodule, the developers have to take care not to forget rosetta.

The contents of src/dsp_tools/import_scripts need not be part of the distribution, because the users of DSP-TOOLS will access these files via GitHub, and not via the distributed code. For this reason, this folder is excluded in pyproject.toml.

Passively using the contents of the submodule

If you don't have a clone of DSP-TOOLS yet, clone it with 

git clone --recurse-submodules https://github.com/dasch-swiss/dsp-tools.git

After cloning it that way, and after some time has passed, you might want to get the latest changes from GitHub:

cd dsp-tools
git pull --recurse-submodules

These two commands take care of the submodule, so that its contents are cloned/pulled as well.

In case you have an old clone of DSP-TOOLS, without the submodule, and you want to update it, you have to proceed differently: 

cd dsp-tools
git pull
git submodule update --init --recursive

Some notes: - git clone --recurse-submodules <repo> is shorthand for git clone <repo>; cd <repo>; git submodule update --init --recursive - git pull --recurse-submodules is shorthand for git pull; git submodule update --init --recursive - --init is necessary if you don't have the submodule src/dsp_tools/import_scripts yet. In all successive calls, when the submodule is already on your machine, the flag --init can be omitted. - --recursive is optional, in case there would be more than one (nested) submodules in the repository. - Since Git 2.15, you can tell Git to use --recurse-submodules for all commands that support it (except clone), with git config submodule.recurse true. - These explanations rely on the Git Submodules documentation

Renaming a parent directory of the submodule

Renaming a parent directory of the submodule should be done with git mv old-name new-name, so that git won't be confused that the path to the submodule changed. If this doesn't help, it might be necessary to manually modify

  • the gitdir in src/dsptools/import_scripts/.git
  • the path in .gitmodules, and the name of the submodule in the title of that file
  • the worktree entry in .git/modules/src/dsptools/import_scripts/config and the affected folder names in the path containing that file

Actively working with the contents of the submodule

After retrieving the contents of a submodule as described in the paragraph above, it is in "detached HEAD" state. Before committing to it, the main branch needs to be checked out. The order how to proceed is the following:

cd src/dsp_tools/import_scripts
git checkout main                     # check out main branch of 0123-import-scripts
# (modify contents of submodule)
git add .
git commit -m "modify submodule"
git push origin main                  # push to origin of 0123-import-scripts
cd ../../..
git add src/dsp_tools/import_scripts
git commit -m "modify submodule"
git push origin feature-branch        # push to origin of dsp-tools

When switching between branches, there are two options:

  1. By default (submodule.recurse is false AND branches are switched with git checkout <branch>), the contents of submodules will not be updated.
  2. If submodule.recurse has been set to true, OR if branches are switched with git checkout <branch> --recurse-submodules, the contents of submodules will be updated according to the commit recorded in the super-project. If local modifications in a submodule would be overwritten, the checkout will fail.

To quickly switch between branches when you have uncommitted work in the submodule, the first option might be preferable. After merging a Pull Request and switching back to the main branch, the second option might be more suitable. Read more about the checkout options in the official documentation

Last update: 2022-06-10