Merge branch 'fix_detachbranch' of https://github.com/adrianschroeter/osc

Fix/Workaround for "osc detachbranch" in case of a missing link target
(in this case, the _link file is removed; an alternative would be to
fall back to the last working rev). Also improve the Linkinfo.is_link
check.

osc/commandline.py

@@ -2855,7 +2855,14 @@ Please submit there instead, or use --nodevelproject to force direct submission.
             li = Linkinfo()
             li.read(root.find('linkinfo'))
             if li.islink() and li.haserror():
-                raise oscerr.LinkExpandError(project, package, li.error)
+                try:
+                    show_package_meta(apiurl, li.project, li.package)
+                except HTTPError as e:
+                    if e.code == 404:
+                        print("Link target got removed, dropping link. WARNING: latest submissions in link target might be lost!")
+                        delete_files(apiurl, project, package, ['_link'])
+                    else:
+                        raise oscerr.LinkExpandError(project, package, li.error)
             elif not li.islink():
                 print('package \'%s/%s\' is no link' % (project, package), file=sys.stderr)
             else:

osc/core.py

@@ -540,7 +540,7 @@ class Linkinfo:
 
     def islink(self):
         """returns True if the linkinfo is not empty, otherwise False"""
-        if self.xsrcmd5 or self.lsrcmd5:
+        if self.xsrcmd5 or self.lsrcmd5 or self.error is not None:
             return True
         return False