:Account management; notably managing your SSH public keys for read-write developer access.
:Patch review (account sign-up via [http://identity.kde.org/ KDE Identity]), repository browser and other services.
* '''git.kde.org'''
=== Discontinued services ===
The main git server. Should be used only for pushing new commits to a repository over the SSH protocol.
The following services have been discontinued. Usually their role is now provided by other systems, but they typically are missing some important features which the previous systems had. The redesign unfortunately breaks the workflow e.g. in KDevelop which is not yet adapted to the new setup. The culled systems are listed here for reference as they may well still be referenced in older documentation.
* '''anongit.kde.org'''
* '''commits.kde.org'''
Several servers which allow read-only access to the repositories via the git:// and http:// protocols. They are requested to update when anyone pushes to a repo on git.kde.org, so it can be thought of as being always up-to-date.
:Provides Git commit "short URLs", redirecting to the repository browser pages as appropriate ([http://commits.kde.org/324dd0cd/a8d1175f61e678f61b3643c867f212ad26ce6f44 example]).
* '''[http://projects.kde.org/ KDE Projects]''' (projects.kde.org)
* '''[http://projects.kde.org/ KDE Projects]''' (projects.kde.org)
:Central project hub and primary repository browser.
:Central project hub and primary repository browser.
:Replaced by: the sysadmin/repo-metadata repository (metadata information); phabricator.kde.org (browser)
:Alternative repository browser. At present the only way to view personal clones of project repositories and personal scratch repositories ([[#Personal repositories|see below]]), however the former are planned to appear in projects.kde.org in the future.
:The main git server. Should be used only for pushing new commits to a repository over the SSH protocol.
:Patch review (account sign-up via [http://identity.kde.org/ KDE Identity]). [http://techbase.kde.org/Development/Review_Board|Instructions].
:Several servers which allow read-only access to the repositories via the git:// and http:// protocols. They are requested to update when anyone pushes to a repo on git.kde.org, so it can be thought of as being always up-to-date.
* '''commits.kde.org'''
* '''[https://cgit.kde.org/ cgit.kde.org]'''
:Provides Git commit "short URLs", redirecting to [http://projects.kde.org/ KDE Projects] and [http://gitweb.kde.org/ gitweb.kde.org] pages as appropriate ([http://commits.kde.org/324dd0cd/a8d1175f61e678f61b3643c867f212ad26ce6f44 example]).
:Repository browser. It shows also personal clones of project repositories and personal scratch repositories ([[#Personal repositories|see below]]),.
:Patch review (account sign-up via [http://identity.kde.org/ KDE Identity]). [[Infrastructure/Phabricator|Phabricator]], repository browser, calendar and other services. Phabricator is currently being replaced by Invent and only the workboard component has not been migrated to Invent yet.
:Sends an email with each commit for the projects you want to watch.
== How to get read-write developer access ==
== How to get read-write developer access ==
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== Information For KDE Developers ==
== Information For KDE Developers ==
You can find general information about using Git as a KDE Developer on the [http://techbase.kde.org/Development/Git KDE Git] page on TechBase.
For general information visit the page about [[Infrastructure/Git | the use of Git by KDE]].
To configure Git for your KDE Development environment, please see the [http://techbase.kde.org/Development/Git/Configuration KDE Git Configuration] page on TechBase.
To configure Git for your KDE Development environment, please see the [http://techbase.kde.org/Development/Git/Configuration KDE Git Configuration] page on TechBase.
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You can find some simple step-by-step recipes for using the KDE Git repositories on the [http://techbase.kde.org/Development/Git/Recipes KDE Git Recipes] page on TechBase.
You can find some simple step-by-step recipes for using the KDE Git repositories on the [http://techbase.kde.org/Development/Git/Recipes KDE Git Recipes] page on TechBase.
== Overview of repository URL schemes ==
== Some notes about repository URLs ==
=== URL prefixes ===
=== URL prefixes ===
(KDevelop 5.x users please note: If you came here via the link in KDevelop, note that KDE projects has been '''discontinued''' and replaced by ''Invent''. So the neat automatic import of KDE projects ''no longer works'' and you have to do everything manually instead. Sorry!)
Anonymous read-only access uses the following URL prefix:
git://anongit.kde.org/
Read-write developer access uses this prefix instead:
Following the prefix, here are the path schemes for different types of repositories:
* '''<project identifier>'''
:A KDE project repository, be it part of the KDE SC, KDE Extragear or KDE Playground.
* '''websites/<address sans leading www. and dots replaced by dashes>'''
:A KDE website project, e.g. websites/projects-kde-org.
* '''sysadmin/<repository name>'''
:Non-public repositories used by KDE's sysadmin team.
* '''clones/<original repository path>/<KDE Identity user name>/<user-chosen repository name>'''
:Personal clones of project repositories, e.g. <tt>clones/konversation/hein/morecowbell</tt> or <tt>clones/websites/projects-kde-org/hein/pluginwork</tt> ([[#Personal clones of project repositories|more below]]).
* '''scratch/<KDE identity user name>/<user-chosen repository name>'''
:Personal scratch repositories are a means to start a new project or just to store your favorite .bashrc in a safe location: anything is allowed so long as it is related to KDE or your work for KDE in some way ([[#Personal scratch repositories|more below]]).
=== Let Git rewrite URL prefixes ===
=== Let Git rewrite URL prefixes ===
Instead of remembering the above URL prefixes, you can also put the following in your <tt>~/.gitconfig</tt>:
Instead of remembering URL prefixes, you can also put the following in your <tt>~/.config/git/config</tt>:
[url "git://anongit.kde.org/"]
[url "https://invent.kde.org/"]
insteadOf = kde:
insteadOf = kde:
[url "git@git.kde.org:"]
[url "ssh://git@invent.kde.org/"]
pushInsteadOf = kde:
pushInsteadOf = kde:
If you are in a corporate environment (e.g. behind a firewall) which only allows Ports 80 (HTTP) and 443 (HTTPS), use the following configuration instead (i.e. substitute git:// for http://):
[url "http://anongit.kde.org/"]
insteadOf = kde:
Then, to clone e. g. the Amarok repo, just do
Then, to clone e. g. the Amarok repo, just do
$ git clone kde:amarok
$ git clone kde:multimedia/amarok.git
By using the <tt>kde:</tt> prefix, read access will automatically happen over Git, and authenticated SSH is only required for pushes. Since commits are mirrored to anongit right when you push them, you will not have to worry about anongit being outdated.
== Server-side commands ==
git.kde.org understands several server-side commands that can be used on the command line via SSH in this fashion:
:Shows a table of repository paths and path patterns you have the permission to see along with details about your access rights to them.
:A brief legend for the permission flags shown in the listing:
:* '''@R''' - Read permissions.
:* '''@W''' - Write permissions.
:* '''@C''' - Create permissions (e.g. the initial push to a newly-created repo).
:If you want to list actual repositories corresponding to patterns listed by <tt>info</tt>, such as your personal [[#Personal scratch repositories|scratch repositories]], see the <tt>[[#expand|expand]]</tt> command described next.
:Like <tt>[[#info|info]]</tt> above, but actually walks through the repositories to verify the information. It's much slower as a result, and should be used if <tt>info</tt> doesn't provide enough information. For example, <tt>info</tt> will list your personal [[#Personal scratch repositories|scratch space]] only in the form of a pattern while <tt>expand</tt> can list the actual repositories located there.
:The output is limited to about 20 rows. The optional regex parameter allows you to filter the listing.
:Used to delete a personal clone of a project repository or a personal scratch repository. Requires the repository to be unlocked first using the <tt>[[#unlock|unlock]]</tt> command and will additionally ask for confirmation. See also the <tt>[[#trash|D trash]]</tt> command as an alternative to outright and irrevocable deletion.
:Moves a repository to the personal trash area, creating an entry in the form <tt><repository path>/<timestamp></tt> there. The timestamps, which have second precision, make it possible to have more than one version of a repository in the trash area at the same time.
:<span style="color:red">'''Note:'''</span> Entries in the personal trash area are automatically removed after 28 days!
*'''<span id="restore">D restore <trash area entry></span>''' <small>[[#restore|(link here)]]</small>
:Restores an entry from the personal trash area (see the <tt>[[#list-trash|list-trash]]</tt> command below for how to list the contents of your personal trash area).
:<tt>restore</tt> will deny restoring an entry if doing so would overwrite an existing repository.
:Available only to repository and system administrators, this command enables several hook scripts that git.kde.org will then execute during a push operation to the specified project repository. Importantly, it also enables write access for non-administrators, which is otherwise disabled along with the hooks scripts.
:The hook scripts in question are the ones reponsible for forwarding commits to the [https://mail.kde.org/mailman/listinfo/kde-commits kde-commits] mailing list and [http://www.cia.vc/ CIA.vc], and for processing commit message keywords (BUG, CCMAIL, etc.) that may interact with [http://bugs.kde.org/ KDE Bugzilla] or cause further emails to be sent. As these hook scripts are only available to project repositories, and not to [[#Personal repositories|personal repositories]], the command only applies to them.
:After creating a new, empty project repository for you the system administators will initially disable the hook scripts so you can safely import large numbers of old commits.
===Commands for system administrators===
*'''<span id="sudo">sudo <KDE Identity user name> <command></span>''' <small>[[#sudo|(link here)]]</small>
:Used by system administrators to run one of the above as another user.
:Disables the hook scripts git.kde.org normally executes during a push operation to a project repository. While the hook scripts are disabled only repository administrators can push commits to a repository. Both system and repository administrators have the ability to reenable the hook scripts using the <tt>[[#hooks-enable|hooks enable]]</tt> command.
:Used by system administrators to recover deleted branches or mistaken force pushes (rewinds).
== Commit hook keywords ==
== Commit hook keywords ==
When you commit changes to Git you will be asked for a description of your commit. There are several special keywords defined that you can use in this description. These keywords are always in uppercase.
The following keywords are pseudo-headers - they have to appear at the start of a line and be followed by a colon:
* '''FEATURE:''' [''<bugnumber>'']<br/>Marks the feature as implemented by CC'ing the commit message to <bugnumber>[email protected]. This keyword will also be used to automatically extract entries for the release changelog, so it makes sense to use it for new features even if you don't have a bugnumber for the feature.
* '''BUG:''' ''<bugnumber>''<br/>Marks the bug as fixed by CC'ing the commit message to <bugnumber>[email protected]. This keyword will also be used to automatically extract entries for the release changelog. To use this feature, you need to create a user on [https://bugs.kde.org kde bugs] with a same email and request for bug edit permission through a [http://sysadmin.kde.org/tickets/ KDE Sysadmin ticket].
* '''FIXED-IN:''' ''<version>''<br/>If the '''BUG''' keyword is used to close a bug, this keyword will update the bug's ''release version'' (''Version Fixed In'' field) that the fix appears in. You can only select one version, so prefer the lowest release version that will actually have the fix.
* '''CCBUG:''' ''<bugnumber>''<br/>CC's to the bugreport by sending mail to <bugnumber>@bugs.kde.org. This will '''not''' close the bug.
* '''CCMAIL:''' ''<email-address>''<br/>CC's to the given e-mail address. Used to notify other developers, usually the maintainers of your commit.
See [[Policies/Commit_Policy#Special_keywords_in_GIT_and_SVN_log_messages | Special keywords in GIT and SVN log messages]]
* '''REVIEW:''' ''<reviewnumber>''<br />Closes the review on KDE Reviewboard and adds a comment which refers to the commit.
* '''GUI:'''<br/>Indicates a user visible change in the user interface. This is used to make the documentation team aware of such changes.
* '''DIGEST:'''<br/>Notifies the KDE Commit Digest team of interesting/important commits to look at (for easy collection, summarization and presentation of commits to end-users).
These keyword can appear anywhere on a line:
<br/>(should the svn stuff be removed from this article?)--[[User:Sreich|Sreich]] 04:07, 27 December 2011 (UTC)
* '''SVN_SILENT'''<br/>Marks the commit message "silent" by adding "(silent)" to the subject of the mail to allow filtering out trivial commits. Use this tag carefully and only for really uninteresting, uncontroversial commits.
* '''GIT_SILENT'''<br/> Same as SVN_SILENT
* '''SVN_MERGE'''<br/>Special keyword for people that use the svnmerge script. Marks the commit message as being a merge commit by adding "(merge)" to the subject of the mail. This way receivers can filter out mails that are caused by merging the same patch from one branch to another branch. Reviews of those mails is usually not needed. This keyword filters out the endless property changes used by this script.
== Personal repositories ==
== Personal repositories ==
git.kde.org currently offers two types of personal repositories: Personal clones of project repositories and personal scratch repositories.
invent.kde.org currently offers two types of personal repositories: Personal clones of project repositories and personal repositories.
=== Personal clones of project repositories ===
=== Personal clones of project repositories ===
A personal clone of a project repository can be created using the server-side <tt>clone</tt> command on the command line:
A personal clone of a project repository can be created using the gitlab web interface.
This will create a clone of the source repository in your personal namespace.
This will create a clone of the source repository at <tt>clones/<path to source repository>/<KDE Identity user name>/<clone name></tt>. (See more examples of <tt>clone</tt> in action [[#clone|here]].)
=== Personal repositories ===
This scheme makes it very easy to locate all personal clones of a given project and should be preferred over making one in your personal [[#Personal scratch repositories|scratch space]]. (In fact, the server-side <tt>clone</tt> command won't allow you to clone a project repository into your personal scratch space, but nothing technically prevents you from taking the detour of a local clone to achieve this.)
Personal clones of project repositories currently do not show up on [http://projects.kde.org KDE Projects], but we have plans to change that in the future. Until then, you can use [http://quickgit.kde.org/ quickgit.kde.org] to browse these repositories.
=== Personal scratch repositories ===
Personal scratch repositories are a means to start a new project or just to store your favorite <tt>.bashrc</tt> in a safe location: anything is allowed so long as it is related to KDE or your work for KDE in some way.
Personal scratch repositories are a means to start a new project or just to store your favorite <tt>.bashrc</tt> in a safe location: anything is allowed so long as it is related to KDE or your work for KDE in some way.
For the rest of this instruction, let's assume the following names:
You can create and delete a new personal repository using the gitlab web interface.
* <kde-id> - Your KDE identity user name
* <repo> - Your (new) git repository name
If you start a new project then you need to create a git repository out of it before you start to push it to the scratch repositories. This is done by going into the the directory which will contain your project and type:
git init
This will convert the local directory to a git repository. This is of course not necessary if you already have a local git repo containing your project.
To make pushing to the repository convenient, it is recommended to add a remote to push to first:
Now you need to create something to push. Otherwise git will refuse the next step. So it is recommended that you create a README for your project and then commit that. Afterward, you perform the first push to the repository as follows:
To request your scratch repository be promoted to the status of a KDE Playground project, you currently need to file a [https://go.kde.org/systickets sysadmin repo request]. For details, see the description of an [[Policies/Application Lifecycle|Application Lifecycle]].
git push --all origin
Now your new scratch repository is created and initialized. It will take about 30 minutes until the creation of the new repository has propagated to the other tools and is visible there.
git push --all does not push tags. You can push them in a second step with
git push --tags ...as above...
Personal scratch repositories can be browsed on [http://quickgit.kde.org/ quickgit.kde.org].
You can set a description on your scratch repository by issuing a command
ssh [email protected] desc scratch/<kde-id>/<repo> "Application to do magic"
If you feel your new project is ready for the wider world and/or wish to signal that it welcomes outside contributors, you may wish to promote it to the status of a KDE Playground project. KDE Playground project repositories are located at the top-level, i.e. the repository will be moved out of your scratch space and may have to be renamed in the event of a collision with an existing repository name. KDE Playground projects are featured on [http://projects.kde.org KDE Projects] and covered by the [https://mail.kde.org/mailman/listinfo/kde-commits kde-commits] mailing list (and thus [http://commitfilter.kde.org CommitFilter]), [http://lxr.kde.org/ LXR], the [http://www.englishbreakfastnetwork.org/ EBN] and [http://cia.vc/ CIA], unlike personal scratch repositories.
To request your scratch repository be promoted to the status of a KDE Playground project, you currently need to file a [https://sysadmin.kde.org/tickets/index.php?page=tickets&act=add sysadmin repo request]. In the future we plan to provide a fully automated facility on [http://projects.kde.org KDE Projects].
Note that we have deliberately decided not to allow the direct creation of KDE Playground projects; the path to existence for a KDE Playground repository project always leads through a personal scratch space first. This is to give you the power to decide whether your project is ready, and also to force you to deliberate whether it truly is.
===Deleting personal repositories===
A personal repository can either be deleted outright and irrevocably by using the <tt>[[#destroy|destroy]]</tt> command (which requires you to <tt>[[#unlock|unlock]]</tt> it first to avoid accidental deletion), or you may move it to the personal trash area with the <tt>[[#trash|trash]]</tt> command.
'''Entries in the personal trash area are kept for 28 days,''' and can be resurrected at any moment during those 28 days by way of the <tt>[[#restore|restore]]</tt> command. You can list the current contents of your personal trash area with the <tt>[[#list-trash|list-trash]]</tt> command.
== Using Review Board and post-review ==
A very comfortable way of posting changes for review is [http://git.reviewboard.kde.org Review Board], where every project repository has its own entry. You can read about how to use Git and Review Board on the [http://techbase.kde.org/Development/Review_Board KDE Review Board] page.
Here's an [http://ericholscher.com/blog/2011/jan/24/using-reviewboard-git/ insightful blog post] that explains how to use post-review.
== Requesting project migrations from KDE SVN or Gitorious.org ==
To get your project moved from KDE SVN or Gitorious.org to git.kde.org, you have to file a [http://sysadmin.kde.org/svnaccount/repo-request.php sysadmin request]. It will ask you for the following information:
* The name and description of the project.
* The current location of the project.
* Its current or intended module (e.g. playground/utils or extragear/network).
* Which KDE Identity user name(s) should have admin rights to the repository and the entry on [http://projects.kde.org KDE Projects].
* The email address that the [http://git.reviewboard.kde.org/ ReviewBoard] group for the project should send emails to.
* The date and time the migration should take place (can be "asap").
When we have completed processing your request, there will be an empty repository at the chosen path ([[#Overview of repository URL schemes|more here]]) that the repository administrators can push the data into. (When converting from KDE svn to git this typically involves [[../DeveloperAccessForRuleWriting|writing a rule set]], running svn-all-fast-export, and then pushing the created repository into the new git path.) Once you are done pushing everything to the repository, use the <tt>[[#hooks-enable|hooks enable]]</tt> command to enable the commit hooks and allow write access to non-administrators.
== Advanced Git ==
== Advanced Git ==
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This will preserve commit identities (unless you filter the source repository - see below).
This will preserve commit identities (unless you filter the source repository - see below).
:<span style="color:red">'''Note:'''</span> Before pushing such a merge, talk to [http://sysadmin.kde.org/ sysadmin] (ideally on #kde-sysadmin in irc). They can temporarily disable commit hooks (like CCMAIL and BUG) so that people do not get emails about old commits.
=== Filtering ===
=== Filtering ===
<tt>git filter-branch</tt> allows you to edit history. This is useful when you want to merge only a small part of one repository into another. You can trim the tree, and also alter the commit messages to disable the KDE commit hook keywords, so that the merged history does not cause CCMAILs to be sent for ancient commits.
<tt>git filter-branch</tt> allows you to edit history. This is useful when you want to merge only a small part of one repository into another. You can trim the tree, and also alter the commit messages (for example to add information about the origin of the commits).
A combination of <tt>--tree-filter</tt>, <tt>--prune-empty</tt> and <tt>--msg-filter</tt> generally gets what you want. For example,
A combination of <tt>--tree-filter</tt>, <tt>--prune-empty</tt> and <tt>--msg-filter</tt> generally gets what you want. For example,
--msg-filter 'cat; echo; echo "Commit $GIT_COMMIT in <source-repo>"' \
HEAD
HEAD
This example will remove everything that does not match <tt>foo.*</tt>. Note the <tt>-path</tt> argument to <tt>find</tt> that makes sure you don't delete any of git's own files. <tt>--prune-empty</tt> will remove non-merge commits that no longer have any effect on the tree (you can run <tt>git rebase</tt> after to trim the merge commits if you want). <tt>--msg-filter</tt> neuters the keywords and adds information about where the commit came from (don't forget to change <tt><source-repo></tt>!
This example will remove everything that does not match <tt>foo.*</tt>. Note the <tt>-path</tt> argument to <tt>find</tt> that makes sure you don't delete any of git's own files. <tt>--prune-empty</tt> will remove non-merge commits that no longer have any effect on the tree (you can run <tt>git rebase</tt> after to trim the merge commits if you want). <tt>--msg-filter</tt> adds information about where the commit came from (don't forget to change <tt><source-repo></tt>!)
More complex filters are possible. Have a look at the man page for <tt>git-filter-branch</tt>.
More complex filters are possible. Have a look at the man page for <tt>git-filter-branch</tt>. Note that while you could use the commit message filter to neuter commit hook keywords like CCMAIL, it is better to ask a sysadmin to disable the commit hooks temporarily while you push.
See [http://whileimautomaton.net/2010/04/03012432 mastering git filter-branch: points to extract a subproject] for more helpful hints.
See [http://whileimautomaton.net/2010/04/03012432 mastering git filter-branch: points to extract a subproject] for more helpful hints.
Patch review (account sign-up via KDE Identity), repository browser and other services.
Discontinued services
The following services have been discontinued. Usually their role is now provided by other systems, but they typically are missing some important features which the previous systems had. The redesign unfortunately breaks the workflow e.g. in KDevelop which is not yet adapted to the new setup. The culled systems are listed here for reference as they may well still be referenced in older documentation.
commits.kde.org
Provides Git commit "short URLs", redirecting to the repository browser pages as appropriate (example).
Sends an email with each commit for the projects you want to watch.
git.kde.org
The main git server. Should be used only for pushing new commits to a repository over the SSH protocol.
anongit.kde.org
Several servers which allow read-only access to the repositories via the git:// and http:// protocols. They are requested to update when anyone pushes to a repo on git.kde.org, so it can be thought of as being always up-to-date.
Patch review (account sign-up via KDE Identity). Phabricator, repository browser, calendar and other services. Phabricator is currently being replaced by Invent and only the workboard component has not been migrated to Invent yet.
How to get read-write developer access
KDE developer accounts are managed through KDE Identity. If you already have a KDE SVN developer account, it has been imported into KDE Identity and you may use the Password Reset feature to set a password and manage your SSH public keys. If you don't have a developer account yet, you can request Developer Access in the website's menu upon registering and logging into your account.
To configure Git for your KDE Development environment, please see the KDE Git Configuration page on TechBase.
You can find some simple step-by-step recipes for using the KDE Git repositories on the KDE Git Recipes page on TechBase.
Some notes about repository URLs
URL prefixes
(KDevelop 5.x users please note: If you came here via the link in KDevelop, note that KDE projects has been discontinued and replaced by Invent. So the neat automatic import of KDE projects no longer works and you have to do everything manually instead. Sorry!)
Let Git rewrite URL prefixes
Instead of remembering URL prefixes, you can also put the following in your ~/.config/git/config:
invent.kde.org currently offers two types of personal repositories: Personal clones of project repositories and personal repositories.
Personal clones of project repositories
A personal clone of a project repository can be created using the gitlab web interface.
This will create a clone of the source repository in your personal namespace.
Personal repositories
Personal scratch repositories are a means to start a new project or just to store your favorite .bashrc in a safe location: anything is allowed so long as it is related to KDE or your work for KDE in some way.
You can create and delete a new personal repository using the gitlab web interface.
To request your scratch repository be promoted to the status of a KDE Playground project, you currently need to file a sysadmin repo request. For details, see the description of an Application Lifecycle.
Advanced Git
Safety Precautions
With these techniques, always work on a disposable copy of the repo with all the remotes removed, so if you screw up, it doesn't really matter. Also, work on a separate branch. That way, you can usually use git reset --hard <original-branch> to get back to the starting state.
Also, make sure there are no grafts around (eg: linking to the old kdelibs history in the case of frameworks). The safest way to do this is to use fresh checkouts.
Merging repositories
The git-merge-repo script in kde-dev-scripts can merge the tree and history of one git repository into another.
First, create a commit in the source repo that removes any files you don't want to copy, and rearrange the remaining files to be as you want them to appear in the target repo. It is important the HEAD of the source and target repositories have completely disjoint trees (so you could copy one tree into the other with no file conflicts).
Then go to the root of the target repository and run
/path/to/kde-dev-scripts/git-merge-repo <path to source repo>
This will preserve commit identities (unless you filter the source repository - see below).
Note: Before pushing such a merge, talk to sysadmin (ideally on #kde-sysadmin in irc). They can temporarily disable commit hooks (like CCMAIL and BUG) so that people do not get emails about old commits.
Filtering
git filter-branch allows you to edit history. This is useful when you want to merge only a small part of one repository into another. You can trim the tree, and also alter the commit messages (for example to add information about the origin of the commits).
A combination of --tree-filter, --prune-empty and --msg-filter generally gets what you want. For example,
git filter-branch --prune-empty \
--tree-filter "find -type f -\! -path './.git/*' -\! -name foo.\* -delete" \
--msg-filter 'cat; echo; echo "Commit $GIT_COMMIT in <source-repo>"' \
HEAD
This example will remove everything that does not match foo.*. Note the -path argument to find that makes sure you don't delete any of git's own files. --prune-empty will remove non-merge commits that no longer have any effect on the tree (you can run git rebase after to trim the merge commits if you want). --msg-filter adds information about where the commit came from (don't forget to change <source-repo>!)
More complex filters are possible. Have a look at the man page for git-filter-branch. Note that while you could use the commit message filter to neuter commit hook keywords like CCMAIL, it is better to ask a sysadmin to disable the commit hooks temporarily while you push.
