errors: set detailed exit code to 20 for locking errors

This is per https://www.mercurial-scm.org/wiki/ErrorCategoriesPlan.

Differential Revision: https://phab.mercurial-scm.org/D9242

mercurial/scmutil.py

@@ -159,6 +159,7 b' def callcatch(ui, func):'
     # Global exception handling, alphabetically
     # Mercurial-specific first, followed by built-in and library exceptions
     except error.LockHeld as inst:
+        detailed_exit_code = 20
         if inst.errno == errno.ETIMEDOUT:
             reason = _(b'timed out waiting for lock held by %r') % (
                 pycompat.bytestr(inst.locker)
@@ -172,6 +173,7 b' def callcatch(ui, func):'
         if not inst.locker:
             ui.error(_(b"(lock might be very busy)\n"))
     except error.LockUnavailable as inst:
+        detailed_exit_code = 20
         ui.error(
             _(b"abort: could not lock %s: %s\n")
             % (

tests/test-lock-badness.t

@@ -136,6 +136,6 b' Pushing to a local read-only repo that c'
   pushing to a
   searching for changes
   abort: could not lock repository a: Permission denied
-  [255]
+  [20]
 
   $ chmod 700 a/.hg/store

tests/test-phases-exchange.t

@@ -1327,7 +1327,7 b' error, but EEXIST)'
   waiting for lock on repository $TESTTMP/Upsilon held by ''
   abort: repository $TESTTMP/Upsilon: timed out waiting for lock held by ''
   (lock might be very busy)
-  [255]
+  [20]
   $ rm .hg/store/lock
 
   $ cd ..