Corrects the update document to match the version of gitshell specified in the install document (1.7.1)

It turns out that regex escapes and YAML quoted-scalar escapes don't play
nicely together.

* Show new merge request button from compare page
* Show message if user selected same branches
* Show message if compared branches are the same
* Prepend inputs with from/to labels

SSH is pronounced as /es es aged/, so we need "an" instead of "a".

Trigger notification service when new user-group relation was created

Placeholder in search field was wrong

When viewing the diff for a changed image file, two bugs occur:

- Both the 'before' and 'after' images link to the 'after' commit
- Visiting the link for either image will cause a error

The first is caused by both image links referencing '@commit.id' rather
than '@commit.parent_id'.  The second is caused by the use of
'project_tree_path' which is used for creating links to directories in
the git file tree. 'project_blob_path' which links to files should be
used instead.