Restrict WIP branches name to the one prefixed by `wip/` only.

wiki/src/contribute/git.mdwn

@@ -174,12 +174,11 @@ should be forked off the devel branch.
 
 If you intend to work on a branch not really meant to be proposed to a
 merge at first, like an experimenting branch that you still want to push
-to share with other developers, you can add the keyword `wip` or `WIP`
-after the topic prefix explained above (e.g `feature/wip-*`). It will
-make it clear to everyone that this branch shouldn't be merged before
-being renamed, and our Jenkins instance will not build and test it, so
-you won't get notifications for a branch that you know is breaking the
-build and/or the test suite.
+to share with other developers, you can prefix its name by the keyword
+`wip/`.  It will make it clear to everyone that this branch shouldn't be
+merged before being renamed, and our Jenkins instance will not build nor
+test it, so you won't get notifications for a branch that you know is
+breaking the build and/or the test suite.
 
 #### experimental