Mercurial > public > mercurial-scm > hg-stable

diff mercurial/revset.py @ 32719:f75d0aa5dc83

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revset: lookup descendents for negative arguments to ancestor operator Negative offsets to the `~` operator now search for descendents. The search is aborted when a node has more than one child as we do not have a definition for 'nth child'. Optionally we can introduce such a notion and take the nth child ordered by rev number. The current revset language does provides a short operator for ancestor lookup but not for descendents. This gives user a simple revset to move to the previous changeset, e.g. `hg up '.~1'` but not to the 'next' changeset. With this change userse can now use `.~-1` as a shortcut to move to the next changeset. This fits better into allowing users to specify revisions via revsets and avoiding the need for special `hg next` and `hg prev` operations. The alternative to negative offsets is adding a new operator. We do not have many operators in ascii left that do not require bash escaping (',', '_', and '/' come to mind). If we decide that we should add a more convenient short operator such as ('/', e.g. './1') we can later add it and allow ascendents lookup via negative numbers.
author David Soria Parra <davidsp@fb.com>
date Sat, 27 May 2017 10:25:09 -0700
parents af854b1b36f8
children 573b792872c1
line wrap: on
line diff
--- a/mercurial/revset.py	Tue Jun 06 22:17:39 2017 +0530
+++ b/mercurial/revset.py	Sat May 27 10:25:09 2017 -0700
@@ -379,12 +379,33 @@
     # Like ``ancestors(set)`` but follows only the first parents.
     return _ancestors(repo, subset, x, followfirst=True)
 
+def _childrenspec(repo, subset, x, n, order):
+    """Changesets that are the Nth child of a changeset
+    in set.
+    """
+    cs = set()
+    for r in getset(repo, fullreposet(repo), x):
+        for i in range(n):
+            c = repo[r].children()
+            if len(c) == 0:
+                break
+            if len(c) > 1:
+                raise error.RepoLookupError(
+                    _("revision in set has more than one child"))
+            r = c[0]
+        else:
+            cs.add(r)
+    return subset & cs
+
 def ancestorspec(repo, subset, x, n, order):
     """``set~n``
     Changesets that are the Nth ancestor (first parents only) of a changeset
     in set.
     """
     n = getinteger(n, _("~ expects a number"))
+    if n < 0:
+        # children lookup
+        return _childrenspec(repo, subset, x, -n, order)
     ps = set()
     cl = repo.changelog
     for r in getset(repo, fullreposet(repo), x):