As mentioned previously I am working toward getting Gitano into Stretch. A colleague and friend of mine (Richard Maw) did a large pile of work on Lace to support what we are calling sub-defines. These let us simplify Gitano's ACL files, particularly for individual projects.

In this posting, I'd like to cover what has changed with the access control support in Gitano, so if you've never used it then some of this may make little sense. Later on, I'll be looking at some better user documentation in conjunction with another friend of mine (Lars Wirzenius) who has promised to help produce a basic administration manual before Stretch is totally frozen.

Sub-defines

With a more modern lace (version 1.3 or later) there is a mechanism we are calling 'sub-defines'. Previously if you wanted to write a ruleset which said something like "Allow Steve to read my repository" you needed:

define is_steve user exact steve
allow "Steve can read my repo" is_steve op_read

And, as you'd expect, if you also wanted to grant read access to Jeff then you'd need yet set of defines:

define is_jeff user exact jeff
define is_steve user exact steve
define readers anyof is_jeff is_steve
allow "Steve and Jeff can read my repo" readers op_read

This, while flexible (and still entirely acceptable) is wordy for small rulesets and so we added sub-defines to create this syntax:

allow "Steve and Jeff can read my repo" op_read [anyof [user exact jeff] [user exact steve]]

Of course, this is generally neater for simpler rules, if you wanted to add another user then it might make sense to go for:

define readers anyof [user exact jeff] [user exact steve] [user exact susan]
allow "My friends can read my repo" op_read readers

The nice thing about this sub-define syntax is that it's basically usable anywhere you'd use the name of a previously defined thing, they're compiled in much the same way, and Richard worked hard to get good error messages out from them just in case.

No more auto_user_XXX and auto_group_YYY

As a result of the above being implemented, the support Gitano previously grew for automatically defining users and groups has been removed. The approach we took was pretty inflexible and risked compilation errors if a user was deleted or renamed, and so the sub-define approach is much much better.

If you currently use auto_user_XXX or auto_group_YYY in your rulesets then your upgrade path isn't bumpless but it should be fairly simple:

  1. Upgrade your version of lace to 1.3
  2. Replace any auto_user_FOO with [user exact FOO] and similarly for any auto_group_BAR to [group exact BAR].
  3. You can now upgrade Gitano safely.

No more 'basic' matches

Since Gitano first gained support for ACLs using Lace, we had a mechanism called 'simple match' for basic inputs such as groups, usernames, repo names, ref names, etc. Simple matches looked like user FOO or group !BAR. The match syntax grew more and more arcane as we added Lua pattern support refs ~^refs/heads/${user}/. When we wanted to add proper PCRE regex support we added a syntax of the form: user pcre ^/.+?... where pcre could be any of: exact, prefix, suffix, pattern, or pcre. We had a complex set of rules for exactly what the sigils at the start of the match string might mean in what order, and it was getting unwieldy.

To simplify matters, none of the "backward compatibility" remains in Gitano. You instead MUST use the what how with match form. To make this slightly more natural to use, we have added a bunch of aliases: is for exact, starts and startswith for prefix, and ends and endswith for suffix. In addition, kind of match can be prefixed with a ! to invert it, and for natural looking rules not is an alias for !is.

This means that your rulesets MUST be updated to support the more explicit syntax before you update Gitano, or else nothing will compile. Fortunately this form has been supported for a long time, so you can do this in three steps.

  1. Update your gitano-admin.git global ruleset. For example, the old form of the defines used to contain define is_gitano_ref ref ~^refs/gitano/ which can trivially be replaced with: define is_gitano_ref ref prefix refs/gitano/
  2. Update any non-zero rulesets your projects might have.
  3. You can now safely update Gitano

If you want a reference for making those changes, you can look at the Gitano skeleton ruleset which can be found at https://git.gitano.org.uk/gitano.git/tree/skel/gitano-admin/rules/ or in /usr/share/gitano if Gitano is installed on your local system.

Next time, I'll likely talk about the deprecated commands which are no longer in Gitano, and how you'll need to adjust your automation to use the new commands.