convert: keep converted hg parents that are outside convert.hg.revs (BC)

Before, when converting revisions without also including their already
converted parents in convert.hg.revs, the parents would no longer be parents.

That seems unfortunate and we dare to assume that nobody ever wants that.

Instead, preserve parents that are outside the current convert range but
already have been converted.

The parents returned in getcommit() are unconditionally converted, so we
introduce a separate optparents with optional parents.

hgext/convert/common.py

@@ -55,11 +55,13 b" SKIPREV = 'SKIP'"
 
 class commit(object):
     def __init__(self, author, date, desc, parents, branch=None, rev=None,
-                 extra={}, sortkey=None, saverev=True, phase=phases.draft):
+                 extra={}, sortkey=None, saverev=True, phase=phases.draft,
+                 optparents=None):
         self.author = author or 'unknown'
         self.date = date or '0 0'
         self.desc = desc
-        self.parents = parents
+        self.parents = parents # will be converted and used as parents
+        self.optparents = optparents or [] # will be used if already converted
         self.branch = branch
         self.rev = rev
         self.extra = extra

hgext/convert/convcmd.py

@@ -472,6 +472,9 b' class converter(object):'
             parents = [self.map.get(p, p) for p in parents]
         except KeyError:
             parents = [b[0] for b in pbranches]
+            parents.extend(self.map[x]
+                           for x in commit.optparents
+                           if x in self.map)
         if len(pbranches) != 2:
             cleanp2 = set()
         if len(parents) < 3:

hgext/convert/hg.py

@@ -582,7 +582,9 b' class mercurial_source(common.converter_'
 
     def getcommit(self, rev):
         ctx = self._changectx(rev)
-        parents = [p.hex() for p in self._parents(ctx)]
+        _parents = self._parents(ctx)
+        parents = [p.hex() for p in _parents]
+        optparents = [p.hex() for p in ctx.parents() if p and p not in _parents]
         crev = rev
 
         return common.commit(author=ctx.user(),
@@ -591,6 +593,7 b' class mercurial_source(common.converter_'
                              desc=ctx.description(),
                              rev=crev,
                              parents=parents,
+                             optparents=optparents,
                              branch=ctx.branch(),
                              extra=ctx.extra(),
                              sortkey=ctx.rev(),

tests/test-convert-hg-startrev.t

@@ -222,7 +222,7 b' Convert from specified revs'
   o  0 "0: add a b f" files: a b f
   
 Convert in multiple steps that doesn't overlap - the link to the parent is
-currently missing
+preserved anyway
 
   $ hg convert --config convert.hg.revs=::1 source multistep
   initializing destination multistep repository
@@ -237,8 +237,8 b' currently missing'
   converting...
   0 2: copy e from a, change b
   $ glog multistep
-  o  2 "2: copy e from a, change b" files: a b c d e
-  
+  o  2 "2: copy e from a, change b" files: b e
+  |
   o  1 "1: add c, move f to d" files: c d f
   |
   o  0 "0: add a b f" files: a b f