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A remote can have a annexUrl configured, that is used by git-annex instead of its usual url. (Similar to pushUrl.)

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Rather ugly dotted version comparison method, but it does work.

Other code is currently depending on checkAttr forcing absolute filenames
to relative, so keep it doing so.

This is a quick fix, and should sometime be moved elsewhere.

* This version of git-annex only works with git 1.7.7 and newer.
  The breakage with old versions is subtle, and affects
  annex.numcopies .gitattributes settings, so be sure to upgrade git
  to 1.7.7. (Debian package now depends on that version.)
* Don't pass absolute paths to git show-attr, as it started following
  symlinks when that's done in 1.7.7. Instead, use relative paths,
  which show-attr only handles 100% correctly in 1.7.7. Closes: #645046

Unfortunatly I can find no way to work with the old and new gits, as
the old had bugs that require absolute paths, while the new doesn't like
them at all. And the behavior of git show-attr in 1.7.7. is the same as
eg, git add of an absolute path to a symlink, so seems entirely
intentional and not likely to change.

Another process may stage journalled files before the lock is
taken, so need to get the list of journalled files afterwards.

It's unfortunate this means getting the directory contents twice,
but it seems better to do that than sometimes take the lock
unnecessarily.

Now supports git's insteadOf configuration, to modify the url used to access a remote. Note that pushInsteadOf is not used; that and pushurl are reserved for actual git pushes. Closes: #644278

And a theoretical fix to branchstate cache invalidation, but not a bug
that could actually happen.

It was checking if it needed to merge on every branch access, fix it to
only check once.

avoids git warning "error: duplicate parent xxx ignored"

only write index once

* git-annex now asks git-annex-shell to verify that it's operating in
  the expected repository.
* Note that this git-annex will not interoperate with remotes using
  older versions of git-annex-shell.

The reason for this check is to avoid git-annex getting confused about
what remote repository actually contains a value. It's a prerequisite for
supporting git insteadOf aliases.

* New or changed repository descriptions in uuid.log now have a timestamp,
  which is used to ensure the newest description is used when the uuid.log
  has been merged.
* Note that older versions of git-annex will display the timestamp as part
  of the repository description, which is ugly but otherwise harmless.

(but not test suite build failure)