fetch2/git: Stop git from triggering fsync() calls

We only ever clone other repositories, if there were a problem such as power
failure, we'd blow away data and rebuild. As such we don't need fsync(). With
filesystems like ext*, the fsync pushes nearly all the data out to disk
which impacts all running processes.

We therefore set a configuration parameter to disable the fsync() calls.

Also fixup a case where basecmd wasn't being used for no good reason.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
fetch2: Cleanup file checksum generation

Cleanup the fix done in f9416e76e272ba3249abff099f6f3a47fe82e03e.

Instead of adding continue statements we can just move the last
statements into the final else-clause.

Signed-off-by: Jacob Kroon <jacob.kroon@mikrodidakt.se>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
bitbake-diffsigs: Fix runtime error when no arguments are given

If bitbake-diffsigs is run without arguments it will error:

    Traceback (most recent call last):
      File "./bin/bitbake-diffsigs", line 121, in <module>
        if output:
    NameError: name 'output' is not defined

Fix this by moving the check for output into the inner else-clause.

Signed-off-by: Jacob Kroon <jacob.kroon@mikrodidakt.se>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>