merge: add pathconflict merge state

Path conflicts that occur during merges are represented by 'pu' (unresolved)
and 'pr' (resolved) records in the merge state.  These are stored on disk
in 'P' records.

Differential Revision: https://phab.mercurial-scm.org/D774

mercurial/merge.py

@@ -66,6 +66,7 b' class mergestate(object):'
     C: a change/delete or delete/change conflict
     D: a file that the external merge driver will merge internally
        (experimental)
+    P: a path conflict (file vs directory)
     m: the external merge driver defined for this merge plus its run state
        (experimental)
     f: a (filename, dictionary) tuple of optional values for a given file
@@ -79,6 +80,15 b' class mergestate(object):'
     m: driver-resolved files marked -- only needs to be run before commit
     s: success/skipped -- does not need to be run any more
 
+    Merge record states (stored in self._state, indexed by filename):
+    u: unresolved conflict
+    r: resolved conflict
+    pu: unresolved path conflict (file conflicts with directory)
+    pr: resolved path conflict
+    d: driver-resolved conflict
+
+    The resolve command transitions between 'u' and 'r' for conflicts and
+    'pu' and 'pr' for path conflicts.
     '''
     statepathv1 = 'merge/state'
     statepathv2 = 'merge/state2'
@@ -158,7 +168,7 b' class mergestate(object):'
 
                 self._readmergedriver = bits[0]
                 self._mdstate = mdstate
-            elif rtype in 'FDC':
+            elif rtype in 'FDCP':
                 bits = record.split('\0')
                 self._state[bits[0]] = bits[1:]
             elif rtype == 'f':
@@ -354,6 +364,8 b' class mergestate(object):'
         for d, v in self._state.iteritems():
             if v[0] == 'd':
                 records.append(('D', '\0'.join([d] + v)))
+            elif v[0] in ('pu', 'pr'):
+                records.append(('P', '\0'.join([d] + v)))
             # v[1] == local ('cd'), v[6] == other ('dc') -- not supported by
             # older versions of Mercurial
             elif v[1] == nullhex or v[6] == nullhex:
@@ -422,6 +434,15 b' class mergestate(object):'
         self._stateextras[fd] = {'ancestorlinknode': hex(fca.node())}
         self._dirty = True
 
+    def addpath(self, path, frename, forigin):
+        """add a new conflicting path to the merge state
+        path:    the path that conflicts
+        frename: the filename the conflicting file was renamed to
+        forigin: origin of the file ('l' or 'r' for local/remote)
+        """
+        self._state[path] = ['pu', frename, forigin]
+        self._dirty = True
+
     def __contains__(self, dfile):
         return dfile in self._state
 
@@ -445,7 +466,7 b' class mergestate(object):'
         """Obtain the paths of unresolved files."""
 
         for f, entry in self._state.iteritems():
-            if entry[0] == 'u':
+            if entry[0] in ('u', 'pu'):
                 yield f
 
     def driverresolved(self):