posts:git:notes: talk about submodule updates and the branch config option.

diff --git a/posts/Git/notes.org b/posts/Git/notes.org
index 64632ad1b50ce2700e0f0bd90620ca7ffaebb267..9990daaec66e8c5bdfc00f795d80d385955583d3 100644 (file)
--- a/posts/Git/notes.org
+++ b/posts/Git/notes.org
@@ -704,6 +704,28 @@ Publish your updated supermodule.
 
     : $ git push
 
+*** Updating all submodules to follow upstream branches
+
+Submodules are usually in the *detached HEAD* state, as you would get
+by running
+
+    : $ git checkout <SHA>
+
+The foreach command checks out a particular local branch in the
+submodule repository, and pulls any changes from that branch's default
+upstream (=branch.name.remote= and =branch.name.merge= in
+=.git/modules/modname/config=).  The name of the branch to check out
+is extracted from =.gitmodules=, so you'll want to manually specify
+your intended branch (e.g. after adding a new submodule):
+
+     : $ git submodule add -b xyz git://example.com/abc.git somedir
+     : $ git config -f .gitmodules submodule.somedir.branch xyz
+
+Once you've done that for each of your submodules, you can (since Git
+version 1.7.2, commit f030c96d) run
+
+    : $ git submodule foreach 'git checkout $(git config --file $toplevel/.gitmodules submodule.$name.branch) && git pull'
+
 *** Removing submodules
 From the [[http://git.or.cz/gitwiki/GitSubmoduleTutorial][Git Wiki]]