buildhistory-diff: operate from buildhistory directory

If the cwd is named "buildhistory" and the user hasn't specified an
alternative path on the command line, then assume that the current
directory is the buildhistory directory. This makes it easier to run
buildhistory-diff and also interact with the buildhistory git repository
as you no longer have to jump into the buildhistory directory and up to
the parent again when doing so.

(From OE-Core rev: e4ccec2e4c2f521a2bb473083b42aefd494eea23)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/buildhistory-diff

@@ -45,6 +45,11 @@ def main():
         sys.stderr.write("Version of GitPython is too old, please install GitPython (python-git) 0.3.1 or later in order to use this script\n")
         sys.exit(1)
 
+    if not os.path.exists(options.buildhistory_dir):
+        if options.buildhistory_dir == 'buildhistory/':
+            cwd = os.getcwd()
+            if os.path.basename(cwd) == 'buildhistory':
+                options.buildhistory_dir = cwd
     if not os.path.exists(options.buildhistory_dir):
         sys.stderr.write('Buildhistory directory "%s" does not exist\n\n' % options.buildhistory_dir)
         parser.print_help()