[PATCH 2 of 2 V2] rebase: calculate ancestors for --base separately (issue5420)

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1479426495 0
#      Thu Nov 17 23:48:15 2016 +0000
# Node ID e5451a607d1ca53b2446ab049375e5dd5a055bb8
# Parent  87e0edc93d87b88e2925877469d8c142e01737fc
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r e5451a607d1c
rebase: calculate ancestors for --base separately (issue5420)

Previously, the --base option only works with a single "branch" - if there
are multiple branching points, "rebase" will error out with:

  abort: source is ancestor of destination

This happens if the user has multiple draft branches with different
branching points, and uses "hg rebase -b 'draft()' -d master". The error
message looks cryptic to users who don't know the implementation detail.

This patch changes the logic to calculate ancestors for each "base" branch
so it would work in the multiple branching points case.

Note: if there are multiple bases where some of them are rebasable, while
some of them aren't because the branching point is the destination, the
current behavior is to abort with "nothing to rebase", which seems wrong.
However, that issue is not introduced by this patch - it exists for "-s" as
well. I have reported it as issue5422 and should be solved separately.

diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -722,10 +722,17 @@ def _definesets(ui, repo, destf=None, sr
             destf = str(dest)
 
-        commonanc = repo.revs('ancestor(%ld, %d)', base, dest).first()
-        if commonanc is not None:
-            rebaseset = repo.revs('(%d::(%ld) - %d)::',
-                                  commonanc, base, commonanc)
-        else:
-            rebaseset = []
+        # calculate ancestors for individual bases
+        realbases = []
+        for b in repo.revs('roots(%ld)', base):
+            # branching point
+            bp = repo.revs('ancestor(%d, %d)', b, dest).first()
+            if bp is None:
+                continue
+            # move b to be the direct child of the branching point
+            b = repo.revs('%d::%d - %d', bp, b, bp).first()
+            if b is not None:
+                realbases.append(b)
+
+        rebaseset = repo.revs('%ld::', realbases)
 
         if not rebaseset:
diff --git a/tests/test-rebase-base.t b/tests/test-rebase-base.t
new file mode 100644
--- /dev/null
+++ b/tests/test-rebase-base.t
@@ -0,0 +1,94 @@
+  $ cat >> $HGRCPATH <<EOF
+  > [extensions]
+  > rebase=
+  > drawdag=$TESTDIR/drawdag.py
+  > 
+  > [phases]
+  > publish=False
+  > 
+  > [alias]
+  > tglog = log -G --template "{rev}: {desc}"
+  > EOF
+
+  $ hg init a
+  $ cd a
+
+  $ hg debugdrawdag <<EOS
+  > g f
+  > |/
+  > e c d
+  > | |/
+  > | b
+  > |/
+  > a
+  > EOS
+
+  $ cd ..
+
+Pick a single base:
+
+  $ cp -a a a1 && cd a1
+  $ hg rebase -b c -d g -q
+  $ hg tglog
+  o  6: d
+  |
+  | o  5: c
+  |/
+  o  4: b
+  |
+  o  3: g
+  |
+  | o  2: f
+  |/
+  o  1: e
+  |
+  o  0: a
+  
+  $ cd ..
+
+Pick a base that is already an descendant of dest:
+
+  $ cp -a a a2 && cd a2
+  $ hg rebase -b g -d e
+  nothing to rebase
+  [1]
+  $ hg rebase -b d -d a
+  nothing to rebase
+  [1]
+  $ hg rebase -b d+c+f+e -d a
+  nothing to rebase
+  [1]
+  $ cd ..
+
+Pick multiple bases (issue5420):
+
+  $ cp -a a a3 && cd a3
+  $ hg rebase -b d+f -d g -q
+  $ hg tglog
+  o  6: f
+  |
+  | o  5: d
+  | |
+  | | o  4: c
+  | |/
+  | o  3: b
+  |/
+  o  2: g
+  |
+  o  1: e
+  |
+  o  0: a
+  
+  $ cd ..
+
+Mixed rebasable and non-rebasable bases (unresolved, issue5422):
+
+  $ cp -a a a4 && cd a4
+  $ hg debugdrawdag <<EOS
+  > h
+  > |
+  > g
+  > EOS
+  $ hg rebase -b d+f+h -d g
+  nothing to rebase
+  [1]