From: "W. Trevor King" <wk...@tremily.us>
There are three branches that submodule folks usually care about:
1. The linked $sha1 in the superproject (set explicitly for every
superproject commit, and thus for every superproject branch).
2. The remote-tracking submodule.<name>.branch that tracks a branch in
upstream submodule.<name>.url repository.
3. The submodule's locally checked out branch, which we currently let
the developer setup by hand, which is integrated with one of the
other two branches by non-checkout update modes.
Git is currently a bit weak on conveniently handling branch #3. "Just
use what the developer has setup" works well for many basic workflows,
but falls short for:
* Cloning-updates, where we currently always setup a detached HEAD.
This is easy to fix if you accept submodule.<name>.branch or the
branch pointed to by the cloned repository's HEAD as a guess, but
this conflates branch #2 and branch #3, which may confuse users.
* Workflows where the preferred #3 branch depends on the superproject
branch. For example, if the remote subproject has only a master
branch, but the local superproject needs to develop several
submodule feature branches simultaneously, you can have a situation
like this:
Superproject branch Submodule branch Subproject branch
=================== ================ =================
master master master
feature-1 feature-1 master
feature-2 feature-2 master
feature-3 feature-2 master
In order to checkout the appropriate submodule branch for a given
superproject branch, we need a way to specify the preferred submodule
branch for a given superproject branch. This commit adds two helper
functions:
* get_current_branch, to determine which superproject branch you're
on, and
* get_local_branch, to determine the preferred submodule branch for
that superproject branch.
The lookup chain for the local-branch is:
1. superproject.<superproject-branch>.local-branch in the submodule's
config (superproject/.git/modules/<submodule-name>/config). This
is where the developer can store local per-superproject-branch
overrides (e.g. if they wanted to use submodule branch feature-1
with superproject branch feature-3).
2. submodule.<submodule-name>.local-branch in the superproject's
config. This is where the developer can store local
cross-superproject-branch overrides (e.g. if they wanted to use
submodule branch master for any superproject branch that didn't
have a per-superproject-branch override).
3. submodule.<submodule-name>.local-branch in the superproject's
.gitmodules file. Because the gitmodules file is stored in the
superproject's versioned tree, it is automatically
superproject-branch-specific. For example:
$ git cat-file -p feature-1:.gitmodules
...
[submodule "submod"]
...
local-branch = feature-1
$ git cat-file -p feature-3:.gitmodules
...
[submodule "submod"]
...
local-branch = feature-2
this is where the project-wide defaults are setup and shared
between developers.
4. The default local-branch is 'master'.
The new get_local_branch function handles the first step in this
chain. The next two steps are already covered by the existing
get_submodule_config.
---
git-submodule.sh | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/git-submodule.sh b/git-submodule.sh
index 2677f2e..56fc3f1 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -220,6 +220,39 @@ get_submodule_config () {
printf '%s' "${value:-$default}"
}
+#
+# Print a submodule's configured local branch name
+#
+# $1 = superproject branch
+# $2 = default (from the superproject's .gitmodules)
+#
+# To be called from the submodule root directory.
+#
+get_local_branch ()
+{
+ superproject_branch="$1"
+ default="${2:-master}"
+ if test -z "${superproject_branch}"
+ then
+ value=""
+ else
+ value=$(git config
superproject."$superproject_branch".local-branch)
+ fi
+ printf '%s' "${value:-$default}"
+}
+
+#
+# Print the currently checked out branch of the current repository
+#
+# $1 = default
+#
+get_current_branch ()
+{
+ default="$1"
+ branch=$(git rev-parse --abbrev-ref HEAD 2>/dev/null) ||
+ branch=""
+ printf '%s' "${branch:-$default}"
+}
#
# Map submodule path to submodule name
--
1.8.5.2.237.g01c62c6
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