Sidebar : Show Author + Timestamp and Subject line in tooltip for Submodule

[goran-w]

In #1307 a tooltip was added for SUBMODULES in the left sidebar, showing the current SHA and submodule URL.

This tooltip also shows a status indication icon/badge : normal, not initialized, modified, revision changed, unmerged.
(Of these, the modified indication is based on a single extra call to git status, checking only those submodules that are initially detected as normal. It does NOT show untracked/unstaged changes, due to the -uno flag being used.)

In addition to the above info in the submodule tooltip, it would be very helpful if it could also show the Author, Timestamp and Subject of the current submodule commit. (This would make it much easier to determine if the submodule is "pointing at" the intended commit in the sub-repo.)

That info could be requested in QuerySubmodules for all the submodules at once, using a single extra call to a variant of git submodule :

git submodule foreach -q 'git log HEAD -1 --format="$sm_path;%aN;%at;%s" || :'

The above command outputs a single-line like this for each submodule:

<submodule-path>;<author-name>;<author-timestamp>;<subject>

Notes on the above command :

• Uninitialized (not checked-out) submodules will be ignored by this command.
• The '|| :' at the end of the "inner" command is added (as recommended in the Git docs) to avoid terminating the foreach processing if the "inner" command returns non-zero.
• The '$sm_path' variable is one of a few provided by the git submodule foreach command.
• The ';' separator can be changed to any separator character/string of choice.