user-manual: miscellaneous editing
user-manual: miscellaneous editing

I cherry-picked some additional miscellaneous fixes from those suggested
by Santi Béjar, including fixes to:

	- correct discussion of repository/HEAD->repository shortcut
	- add mention of git-mergetool
	- add mention of --track
	- mention "-f" as well as "+" for fetch

Cc: Santi Béjar <618d5c06931bb914cb25a8dab62e9b51dbfacc2d@gmail.com>
Signed-off-by: "J. Bruce Fields" <51738506c1b2ccb0761f23bdc612c93babf738ea@citi.umich.edu>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git