====== Working with Git Submodules in MantisBT ======

Some [[3rdpartycode|3rd party libraries]] are stored and maintained in the MantisBT repository 
using [[http://git-scm.com/book/en/Git-Tools-Submodules|Git Submodules]].

This setup requires some special handling when initializing the repository and when switching branches,
especially to and from branches which do not (yet) have submodules in it.

The purpose of this page is to provide basic instructions to easily deal with commonly encountered issues.


===== Initializing the Repository =====

This is covered in the MantisBT Developer's Guide.

@@@TODO - update this when updated docbook has been merged with Master. Until then, copy/paste follows:

===== Switching Branches =====


==== With Submodules --> No Submodules ====

Checking out a branch with Submodules when the current branch does not have them.

<code>
$ git status
# On branch WithSubmodules
nothing to commit, working directory clean

$ git checkout NoSubmodules
error: The following untracked working tree files would be overwritten by checkout:
	(list of files)
Aborting
</code>

**Solution 1**

**WARNING**: this will cause the loss of all changes in any of the submodules that have not been pushed upstream.
Only do this if you are sure that you don't have any pending modifications.

First we force checkout to ignore changes, then we remove all untracked files.

<code>
$ git checkout --force NoSubmodules
warning: unable to rmdir library/adodb: Directory not empty
warning: unable to rmdir library/phpmailer: Directory not empty
Switched to branch 'NoSubmodules'

$ git clean --force
Removing library/adodb/.gitattributes
[...]
Removing library/phpmailer/.gitignore
</code>

**Solution 2**

This is slightly more complex but safer alternative, recommended if there are changes to be kept in the submodules.

Move the submodules directory to a temporary location, e.g. ''/tmp''
<code>
$ sed -rn "s/^.*path\s*=\s*(.*)$/\1/p" .gitmodules |xargs -I{} mv {} /tmp
$ git checkout NoSubmodules
Switched to branch 'NoSubmodules'
</code>

When switching back from the older branch, the submodules directories will be empty. At that point you can either

  * Update the submodules to reclone them (in which case earlier changes will be lost) <code>
$ git submodule update</code>

  * Restore the directories previously moved to ''/tmp'' back into the empty directories, e.g. <code>
sed -rn "s/^.*path\s*=\s*(.*)$/\1/p" .gitmodules |xargs -n 1 basename |xargs -I{} mv -v /tmp/{} library
</code>

==== No Submodules --> With Submodules ====

Checking out a branch without Submodules when the current branch has them.

<code>
$ git status
# On branch NoSubmodules
nothing to commit, working directory clean

$ git checkout WithSubmodules
M	library/adodb
M	library/phpmailer
Switched to branch 'WithSubmodules'
</code>

**Solution**

Use the following command to reset all Submodules to the state of their respective recorded commit:
<code>
git submodule foreach git checkout -- .
</code>



==== Submodules --> Submodules ====

Checking out a branch with Submodules when the current branch has the same submodules but pointing to a different commit.

For example, branch SubmodulesNew has an updated ADOdb library:
<code>
$ git status
# On branch SubmodulesOld
nothing to commit, working directory clean

$ git checkout SubmodulesNew
M	library/adodb
Switched to a new branch 'SubmodulesNew'
</code>

**Solution**

Just update the submodule(s)...

<code>
$ git submodule update 
Submodule path 'library/adodb': checked out '<commit sha>'
</code>







===== Updating a Library's submodule =====

This section describes the process to update a submodule when a new version of a library has been released upstream.

==== Updating via an external repository ====

The example given here are for the ADOdb library, but the same logic should apply (possibly with some variations) to other submodules as well.
We assume that you already have a local repository configured with the appropriate remotes (//upstream// for the library's official repository and //origin// for the MantisBT fork)

  - Update the library's fork in the //mantisbt// Github organization 
    * Get the latest from upstream <code>
cd /path/to/local/adodb
git fetch upstream
</code>
    * Optional: update the //master// branch <code>
git rebase upstream/master master
</code>
    * Update the branch <code>
git checkout mantis-1.3
git merge v5.19
</code>
    * Resolve any conflicts
    * Push changes to the fork <code>
git push origin --tags master mantis-1.3
</code> Note that it's not strictly necessary to push the tags or the master branch. Having the tags allows a better description of the submodule's current commit when running ''git submodule'' (see example at the end of this section)
  - Update the submodule
    * Go to your local mantisbt repository and update it<code>
cd /path/to/mantisbt
git checkout master
git pull
</code>
    * Go to the submodule's directory and checkout the branch <code>
cd library/adodb
git checkout mantis-1.3
git pull
cd ..
</code>
  - Update ''README.libs'' to reflect the new version
  - Commit the changes <code>
git commit -a
</code>

At this point, checking the submodules' status should give you a "clean" list , e.g. (notice no '+' sign in column 1)

<code>
$ git submodule 
 9346d288a1b7f7a50cc35b6a0e56d29e9d000ecf adodb (v5.19-6-g9346d28)
 75a4e5595c0dfcb2e2e1e41b9ba2282828d3f292 disposable (release-2.0.0-3-g75a4e55)
 cb771839899d9f6be9f1268b986c30327ff1199b phpmailer (v5.2.6-2-gcb77183)
 41beaddd279c695aacb63407e2c98b04b7eaff51 securimage (heads/mantis)
</code>

==== Updating from within the submodule ====

It's worth mentioning that step 1 above can also be performed straight from the submodule itself (see example below for phpmailer), provided of course that the remotes (origin and upstream) have been properly configured.

**WARNING**: if you update the submodule in-place, it is critical that you actually push the changes to //origin// otherwise the other developers will have an corrupted repository with missing commits when they pull the changes.

  * Update the submodule from upstream <code>
cd library/phpmailer
git fetch upstream
git rebase upstream/master master
git checkout mantis
git merge v5.2.7
# Resolve conflicts
</code>
  * Push changes to the fork - **don't forget this step !**<code>
git push origin --tags master mantis
cd ..
</code>
  * Edit ''README.libs''
  * Commit the changes <code>
git commit -a
</code>