gitolite/doc/wildcard-repositories.mkd

# repositories named with wildcards

***IMPORTANT NOTE***:

This feature may be somewhat "brittle" in terms of security.  Creating
repositories based on wild cards, giving "ownership" to the specific user who
created it, allowing him/her to hand out R and RW permissions to other users
to collaborate, all these are possible.  And any of these could have a bug in
it.  I haven't found any yet, but that doesn't mean there aren't any.

----

In this document:

  * <a href="#_quick_introduction">quick introduction</a>
  * <a href="#_rc_file_setting_required">rc file setting required</a>
  * <a href="#_examples_of_wildcard_repos">examples of wildcard repos</a>
      * <a href="#_wildcard_repos_with_creator_name_in_them">wildcard repos with creator name in them</a>
      * <a href="#_wildcard_repos_without_creator_name_in_them">wildcard repos without creator name in them</a>
  * <a href="#_side_note_line_anchored_regexes">side-note: line-anchored regexes</a>
      * <a href="#_contrast_with_refexes">contrast with refexes</a>
  * <a href="#_handing_out_rights_to_wildcard_matched_repos">handing out rights to wildcard-matched repos</a>
  * <a href="#_setting_a_gitweb_description_for_a_wildcard_matched_repo">setting a gitweb description for a wildcard-matched repo</a>
  * <a href="#_reporting">reporting</a>
  * <a href="#_how_it_actually_works">how it actually works</a>

----

This document is mostly "by example".

----

<a name="_quick_introduction"></a>

### quick introduction

The wildrepos feature allows you to specify access control rules using regular
expression patterns, so you can have many actual repos being served by a
single set of rules in the config file.  The regex pattern can also include
the word `CREATOR` in it, allowing you to parametrise the name of the user
creating the repo.  The examples below will make this clearer.

<a name="_rc_file_setting_required"></a>

### rc file setting required

This feature requires that you set `$GL_WILDREPOS` to "1" in `~/.gitolite.rc`
on the server.  Please search for that variable and see comments around it in
`conf/example.gitolite.rc` for more information on this.

<a name="_examples_of_wildcard_repos"></a>

### examples of wildcard repos

As the introduction said, you can include the word `CREATOR` in the regex
pattern, though it is not mandatory.  We'll look at examples of both types of
usage.

Which of these alternatives you choose depends on your needs, and the social
aspects of your environment.  Including the creator name in the pattern keeps
users rigidly separated from each others repos, and is good for a largely
autonomous collection of users with a high probability of repo name clashes.

Omitting the creator name from the pattern puts the repos in a common
namespace, and is suitable for environments where it is not very important to
keep track of who actually created the repo (except for granting access), but
needs more communication / co-operation among the users to avoid repo name
clashes.

<a name="_wildcard_repos_with_creator_name_in_them"></a>

#### wildcard repos with creator name in them

Here's an example snippet:

    @prof       =   u1
    @TAs        =   u2 u3
    @students   =   u4 u5 u6

    repo    assignments/CREATOR/a[0-9][0-9]
        C   =   @students
        RW+ =   CREATOR
        RW  =   WRITERS @TAs
        R   =   READERS @prof

For now, ignore the special usernames READERS and WRITERS, and just create a
new repo, as user "u4" (a student):

    $ git clone git@server:assignments/u4/a12
    Initialized empty Git repository in /home/sitaram/t/a12/.git/
    Initialized empty Git repository in /home/gitolite/repositories/assignments/u4/a12.git/
    warning: You appear to have cloned an empty repository.

Notice the *two* empty repo inits, and the order in which they occur ;-)

<a name="_wildcard_repos_without_creator_name_in_them"></a>

#### wildcard repos without creator name in them

Here's how the same example would look if you did not want the CREATOR's name
to be part of the actual repo name.

    repo    assignments/a[0-9][0-9]
        C   =   @students
        RW+ =   CREATOR
        RW  =   WRITERS @TAs
        R   =   READERS @prof

We haven't changed anything except the repo name pattern.  This means that the
first student that creates, say, `assignments/a12` becomes the owner.
Mistakes (such as claiming a12 instead of a13) need to be rectified by an
admin logging on to the back end, though it's not too difficult.

You could also repace the C line like this:

        C   =   @TAs

and have a TA create the repos in advance.

In either case, they could then use the `setperms` feature to specify which
users are "READERS" and which are "WRITERS".  See later for details.

<a name="_side_note_line_anchored_regexes"></a>

### side-note: line-anchored regexes

A regex like

    repo assignments/S[0-9]+/A[0-9]+

would match `assignments/S02/A37`.  It will not match `assignments/S02/ABC`,
or `assignments/S02/a37`, obviously.

But you may be surprised to find that it does not match even
`assignments/S02/A37/B99`.  This is because internally, gitolite
*line-anchors* the given regex; so that regex actually becomes
`^assignments/S[0-9]+/A[0-9]+$` -- notice the line beginning and ending
metacharacters.

<a name="_contrast_with_refexes"></a>

#### contrast with refexes

Just for interest, note that this is in contrast to the refexes for the normal
"branch" permissions, as described in `conf/example.conf` and elsewhere.
These "refexes" are only anchored at the start; a pattern like
`refs/heads/master` actually can match `refs/heads/master01/bar` as well, even
if no one will actually push such a branch!  You can anchor both sides if you
really care, by using `master$` instead of `master`, but that is *not* the
default for refexes.

<a name="_handing_out_rights_to_wildcard_matched_repos"></a>

### handing out rights to wildcard-matched repos

In the examples above, we saw two special "user" names: READERS and WRITERS.
The permissions they have are controlled by the config file, but ***who is
part of this list*** is controlled by the person who created the repository.

The use case is that, although our toy example has only 3 students, in reality
there will be a few dozen, but each assignment will be worked on only by a
handful from among those.  This allows the creator to take ad hoc sets of
users from among the actual users in the system, and place them into one of
two categories (whose permissions are, in this example, R and RW
respectively).  In theory you could do the same thing by creating lots of
little "assignment-NN" groups in the config file but that may be a little too
cumbersome for non-secret environments.

Create a small text file that contains the permissions you desire:

    $ cat > myperms
    R u5
    RW u6
    (hit ctrl-d here)

...and use the new "setperms" command to set permissions for your repo:

    $ ssh git@server setperms assignments/u4/a12 < myperms
    New perms are:
    R u5
    RW u6

'setperms' will helpfully print what the new permissions are but you can also
use 'getperms' to check:

    $ ssh git@server getperms assignments/u4/a12
    R u5
    RW u6

The following points are important:

  * note the syntax of the commands; it's not a "git" command, and there's no
    `:` like in a repo URL.  The first space-separated word is R or RW, and
    the rest are simple usernames.

  * whoever you specify as "R" will match the special user READERS.  "RW" will
    match WRITERS.

<a name="_setting_a_gitweb_description_for_a_wildcard_matched_repo"></a>

### setting a gitweb description for a wildcard-matched repo

Similar to the getperms/setperms commands, there are the getdesc/setdesc
commands, thanks to Teemu.

<a name="_reporting"></a>

### reporting

In order to see what repositories were created from a wildcard, use the
"expand" command, described briefly in [doc/report-output.mkd][repout].

<a name="_how_it_actually_works"></a>

### how it actually works

This section tells you what is happening inside gitolite so you can understand
this feature better.  Let's use the config example at the beginning of this
document:

    repo    assignments/CREATOR/a[0-9][0-9]
        C   =   @students
        RW+ =   CREATOR
        RW  =   WRITERS @TAs
        R   =   READERS @prof

First we find the set of rules to apply.  This involves replacing the special
words CREATOR, WRITERS, and READERS with appropriate usernames to derive an
"effective" ruleset for the repo in question.

For a **new** repo, replace the word CREATOR in all repo patterns and rules
with the name of the invoking user.

>   (Note: this is why you should never use `C = CREATOR`; it becomes `C =
>   invoking_user`!  Unless you really want to allow *all* users to create
>   repos, you should restrict "C" perms to an actual user or set of users,
>   like in the examples in this document).

For an **existing** repo, do the same but replace with the name of the user
who actually *created* the repo (this name is recorded in a special file in
the repo directory when the repo is first created, so it is available).

Now find a repo pattern that matches the actual reponame being pushed -- this
tells you which set of rules to apply.  There can be multiple matches; if so,
they will all be applied in the sequence they appear in the config file.

If the invoking user has been given "RW" permissions using `setperms`, all
occurrences of the word WRITERS are replaced by the invoking username.
Otherwise -- and this includes the "new repo" case, since you couldn't have
run `setperms` on a non-existant repo -- they are replaced by "NOBODY".

(The same thing is done with "R" access and the word "READERS".)

At this point we have an effective ruleset, and the normal access rules (R,
RW, etc) apply, with the addition that the invoking user needs "C" access to
be able to create a repo.

>   (Note: "C" rights do not automatically give the CREATOR any other rights;
>   they must be specifically given.  `RW+ = CREATOR` is recommended in most
>   situations, as you can see in our example).

Assuming user "u4" trying to push-create a new repo called
`assignments/u4/a23`, this is what the effective ruleset looks like (we're
ignoring the "NOBODY" business):

    repo    assignments/u4/a23
        C   =   @students
        RW+ =   u4
        RW  =   @TAs
        R   =   @prof

If u4 gives "RW" perms to u5 using `setperms`, and u5 tries to access that
repo, the ruleset looks like:

    repo    assignments/u4/a23
        C   =   @students
        RW+ =   u4
        RW  =   u5 @TAs
        R   =   @prof

I hope that helps.

----

Enjoy, and please use with care.  This is pretty powerful stuff.  As they say:
if you break it, you get to keep both pieces :)

[repout]: http://github.com/sitaramc/gitolite/blob/pu/doc/report-output.mkd