Fix revision'd checkout of scmsync package

When specifing a revision to a checkout we need to transfer the
information to the bridge to do the right checkout. We also need
to take the former git url in case it has changed meanwhile.

osc/core.py

@@ -3156,8 +3156,25 @@ def checkout_package(
             raise oscerr.OscIOError(None, 'Install the obs-scm-bridge package to work on packages managed in scm (git)!')
         scm_url = scmsync_element.text
         directory = make_dir(apiurl, project, package, pathname, prj_dir, conf.config['do_package_tracking'], outdir)
+
+        if revision is not None:
+            # search for the git sha sum based on the OBS DISTURL package source revision
+            # we need also take into account that the url was different at that point of time
+            url = shasum = None
+            u = makeurl(apiurl, ['source', project, package, '_scmsync.obsinfo'], {'rev': revision})
+            f = http_GET(u)
+            for line in f.readlines():
+                if line.startswith(b"revision: "):
+                    shasum = line[10:].rstrip()
+                if line.startswith(b"url: "):
+                    url = line[5:].rstrip()
+            if shasum is None:
+                raise oscerr.OscIOError(None, 'Unable to find git shasum for given revision')
+            scm_url = url + b'#' + shasum
+
         os.putenv("OSC_VERSION", get_osc_version())
         run_external(['/usr/lib/obs/service/obs_scm_bridge', '--outdir', directory, '--url', scm_url])
+
         Package.init_package(apiurl, project, package, directory, size_limit, meta, progress_obj, scm_url)
 
         # add package to <prj>/.obs/_packages