In Darcs, any command can have a post hook (and a pre hook), and the hook
command can be set using a command-line option to the darcs command that you
run. So, in the Vervis SSH server, if we add a --posthook option when running
`darcs apply` to apply remotely received patches, we get a chance to process
the patch data much like in the git post-receive hook.
The setup this patch creates is similar to the git one: It writes a
_darcs/prefs/defaults file to all Darcs repos, and that defaults file sets the
posthook line for `darcs apply`. The posthook line simply executes the actual
hook program written in Haskell.
The current hook program is a one-liner that prints a line to stdout, so every
time you `darcs push` you can tell the hook got executed. The next step is to
implement the actual hook logic, by reading patch data from the environment
variable in which Darcs puts it.
Here's how it works:
- When Vervis starts, it writes a config file and it writes post-receive hooks
into all the repos it manages
- When a git push is accepted, git runs the post-receive hook, which is a
trivial shell script that executes the actual Haskell program implementing
the hook logic
- The Haskell hook program generates a Push JSON object and HTTP POSTs it to
Vervis running on localhost
- Vervis currently responds with an error, the next step is to implement the
actual publishing of ForgeFed Push activities
