flags: actually merge flags in simplemerge

Since b86fc43e4b73, the local flag were blindly taken. This resulted in bug when
rename are involved. exec flag change are now properly merged (when merged from
the rename side).

Another bug is affecting this when merging from the side without the rename.

Differential Revision: https://phab.mercurial-scm.org/D8533

mercurial/simplemerge.py

@@ -22,7 +22,9 b' from .i18n import _'
 from . import (
     error,
     mdiff,
+    node as nodemod,
     pycompat,
+    util,
 )
 from .utils import stringutil
 
@@ -449,6 +451,17 b' def _picklabels(defaults, overrides):'
     return result
 
 
+def _bytes_to_set(b):
+    """turns a multiple bytes (usually flags) into a set of individual byte"""
+    return set(b[x : x + 1] for x in range(len(b)))
+
+
+def is_null(ctx):
+    if not util.safehasattr(ctx, "node"):
+        return False
+    return ctx.node() != nodemod.nullid
+
+
 def simplemerge(ui, localctx, basectx, otherctx, **opts):
     """Performs the simplemerge algorithm.
 
@@ -503,8 +516,20 b' def simplemerge(ui, localctx, basectx, o'
         else:
             mergedtext += line
 
+    # merge flags if necessary
+    flags = localctx.flags()
+    localflags = _bytes_to_set(flags)
+    otherflags = _bytes_to_set(otherctx.flags())
+    if is_null(basectx) and localflags != otherflags:
+        baseflags = _bytes_to_set(basectx.flags())
+        flags = localflags & otherflags
+        for f in localflags.symmetric_difference(otherflags):
+            if f not in baseflags:
+                flags.add(f)
+        flags = b''.join(sorted(flags))
+
     if not opts.get(b'print'):
-        localctx.write(mergedtext, localctx.flags())
+        localctx.write(mergedtext, flags)
 
     if m3.conflicts and not mode == b'union':
         return 1

tests/test-merge-exec.t

@@ -195,7 +195,6 b' merge them (from the rename side)'
   M z
     a
   $ [ -x z ] || echo "executable bit lost"
-  executable bit lost
 
 merge them (from the chmod side)