template: compute verb in obsfateverb

Add a template function obsfateverb which use the markers information to
compute a better obsfate verb.

The current logic behind the obsfate verb is simple for the moment:

- If the successorsets is empty, the changeset has been pruned, for example:

    Obsfate: pruned

- If the successorsets length is 1, the changeset has been rewritten without
  divergence, for example:

    Obsfate: rewritten as 2:337fec4d2edc, 3:f257fde29c7a

- If the successorsets length is more than 1, the changeset has diverged, for
  example:

    Obsfate: split as 2:337fec4d2edc, 3:f257fde29c7a

As the divergence might occurs on a subset of successors, we might see some
successors twice:

    Obsfate: split as 9:0b997eb7ceee, 5:dd800401bd8c, 10:eceed8f98ffc; split
    as 8:b18bc8331526, 5:dd800401bd8c, 10:eceed8f98ffc

mercurial/obsutil.py

@@ -590,3 +590,14 b' def successorsandmarkers(repo, ctx):'
         values.append({'successors': sset, 'markers': sset.markers})
 
     return values
+
+def successorsetverb(successorset):
+    """ Return the verb summarizing the successorset
+    """
+    if not successorset:
+        verb = 'pruned'
+    elif len(successorset) == 1:
+        verb = 'rewritten'
+    else:
+        verb = 'split'
+    return verb

mercurial/templater.py

@@ -18,6 +18,7 b' from . import ('
     encoding,
     error,
     minirst,
+    obsutil,
     parser,
     pycompat,
     registrar,
@@ -849,6 +850,22 b' def mod(context, mapping, args):'
     func = lambda a, b: a % b
     return runarithmetic(context, mapping, (func, args[0], args[1]))
 
+@templatefunc('obsfateverb(successors)')
+def obsfateverb(context, mapping, args):
+    """Compute obsfate related information based on successors (EXPERIMENTAL)"""
+    if len(args) != 1:
+        # i18n: "obsfateverb" is a keyword
+        raise error.ParseError(_("obsfateverb expects one arguments"))
+
+    successors = evalfuncarg(context, mapping, args[0])
+
+    try:
+        return obsutil.successorsetverb(successors)
+    except TypeError:
+        # i18n: "obsfateverb" is a keyword
+        errmsg = _("obsfateverb first argument should be countable")
+        raise error.ParseError(errmsg)
+
 @templatefunc('relpath(path)')
 def relpath(context, mapping, args):
     """Convert a repository-absolute path into a filesystem path relative to

tests/test-obsmarker-template.t

@@ -13,7 +13,8 b' Global setup'
   > stabilization=all
   > [templates]
   > obsfatesuccessors = " as {join(successors, ", ")}"
-  > obsfate = "rewritten{obsfatesuccessors}; "
+  > obsfateverb = "{obsfateverb(successors)}"
+  > obsfate = "{obsfateverb}{obsfatesuccessors}; "
   > [alias]
   > tlog = log -G -T '{node|short}\
   >     {if(predecessors, "\n  Predecessors: {predecessors}")}\
@@ -318,7 +319,7 b' Predecessors template should show curren'
   o  337fec4d2edc
   |
   | @  471597cad322
-  |/     Obsfate: rewritten as 2:337fec4d2edc, 3:f257fde29c7a;
+  |/     Obsfate: split as 2:337fec4d2edc, 3:f257fde29c7a;
   o  ea207398892e
   
   $ hg up f257fde29c7a
@@ -359,7 +360,7 b' with --hidden'
   o  337fec4d2edc
   |
   | x  471597cad322
-  |/     Obsfate: rewritten as 2:337fec4d2edc, 3:f257fde29c7a;
+  |/     Obsfate: split as 2:337fec4d2edc, 3:f257fde29c7a;
   o  ea207398892e
   
   $ hg fatelogjson --hidden
@@ -1528,7 +1529,7 b' Check templates'
   o  dd800401bd8c
   |
   | x  9bd10a0775e4
-  |/     Obsfate: rewritten as 5:dd800401bd8c, 6:4a004186e638, 7:ba2ed02b0c9a;
+  |/     Obsfate: split as 5:dd800401bd8c, 6:4a004186e638, 7:ba2ed02b0c9a;
   o  f897c6137566
   |
   | x  0dec01379d3b
@@ -1603,7 +1604,7 b' Check templates'
   o  dd800401bd8c
   |
   | @  9bd10a0775e4
-  |/     Obsfate: rewritten as 5:dd800401bd8c, 9:0b997eb7ceee, 10:eceed8f98ffc; rewritten as 5:dd800401bd8c, 8:b18bc8331526, 10:eceed8f98ffc;
+  |/     Obsfate: split as 5:dd800401bd8c, 9:0b997eb7ceee, 10:eceed8f98ffc; split as 5:dd800401bd8c, 8:b18bc8331526, 10:eceed8f98ffc;
   o  f897c6137566
   |
   o  ea207398892e