histedit: add an experimental base action

This is a first (very simple) version of the histedit base action.
It works well in common usecases like rebasing the whole stack and
spliting the stack.

I don't see any obvious edge cases - but probably there is more than one.
That's why I want to keep it behind experimental.histeditng config knob
for now. I think on knob for all new histedit behaviors is better because
we will test all of them together and testers will need to turn it on only
once to get all new nice things.

tests/test-histedit-base.t

@@ -0,0 +1,273 b''
+  $ . "$TESTDIR/histedit-helpers.sh"
+
+  $ cat >> $HGRCPATH <<EOF
+  > [alias]
+  > tglog = log -G --template "{rev}:{node}:{phase} '{desc}'\n"
+  > [extensions]
+  > histedit=
+  > [experimental]
+  > histeditng=True
+  > EOF
+
+Create repo a:
+
+  $ hg init a
+  $ cd a
+  $ hg unbundle "$TESTDIR/bundles/rebase.hg"
+  adding changesets
+  adding manifests
+  adding file changes
+  added 8 changesets with 7 changes to 7 files (+2 heads)
+  (run 'hg heads' to see heads, 'hg merge' to merge)
+  $ hg up tip
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ hg tglog
+  @  7:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  |
+  | o  6:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  |/|
+  o |  5:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  | |
+  | o  4:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  | o  3:32af7686d403cf45b5d95f2d70cebea587ac806a:draft 'D'
+  | |
+  | o  2:5fddd98957c8a54a4d436dfe1da9d87f21a1b97b:draft 'C'
+  | |
+  | o  1:42ccdea3bb16d28e1848c95fe2e44c000f3f21b1:draft 'B'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+
+
+Go to D
+  $ hg update 3
+  3 files updated, 0 files merged, 2 files removed, 0 files unresolved
+edit the history to rebase B onto H
+
+
+Rebase B onto H
+  $ hg histedit 1 --commands - 2>&1 << EOF | fixbundle
+  > base 02de42196ebe
+  > pick 42ccdea3bb16 B
+  > pick 5fddd98957c8 C
+  > pick 32af7686d403 D
+  > EOF
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ hg tglog
+  @  7:0937e82309df47d14176ee15e45dbec5fbdef340:draft 'D'
+  |
+  o  6:f778d1cbddac4ab679d9983c9bb92e4c5e09e7fa:draft 'C'
+  |
+  o  5:3d41b7cc708545206213a842f96d812d2e73d818:draft 'B'
+  |
+  o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  |
+  | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  |/|
+  o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  | |
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+Rebase back and drop something
+  $ hg histedit 5 --commands - 2>&1 << EOF | fixbundle
+  > base cd010b8cd998
+  > pick 3d41b7cc7085 B
+  > drop f778d1cbddac C
+  > pick 0937e82309df D
+  > EOF
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ hg tglog
+  @  6:476cc3e4168da2d036b141f7f7dcff7f8e3fe846:draft 'D'
+  |
+  o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+Split stack
+  $ hg histedit 5 --commands - 2>&1 << EOF | fixbundle
+  > base cd010b8cd998
+  > pick d273e35dcdf2 B
+  > base cd010b8cd998
+  > pick 476cc3e4168d D
+  > EOF
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ hg tglog
+  @  6:d7a6f907a822c4ce6f15662ae45a42aa46d3818a:draft 'D'
+  |
+  | o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |/
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+Abort
+  $ echo x > B
+  $ hg add B
+  $ hg commit -m "X"
+  $ hg tglog
+  @  7:591369deedfdcbf57471e894999a70d7f676186d:draft 'X'
+  |
+  o  6:d7a6f907a822c4ce6f15662ae45a42aa46d3818a:draft 'D'
+  |
+  | o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |/
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+  $ hg histedit 6 --commands - 2>&1 << EOF | fixbundle
+  > base d273e35dcdf2 B
+  > drop d7a6f907a822 D
+  > pick 591369deedfd X
+  > EOF
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  merging B
+  warning: conflicts while merging B! (edit, then use 'hg resolve --mark')
+  Fix up the change and run hg histedit --continue
+  $ hg histedit --abort | fixbundle
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg tglog
+  @  7:591369deedfdcbf57471e894999a70d7f676186d:draft 'X'
+  |
+  o  6:d7a6f907a822c4ce6f15662ae45a42aa46d3818a:draft 'D'
+  |
+  | o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |/
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+Continue
+  $ hg histedit 6 --commands - 2>&1 << EOF | fixbundle
+  > base d273e35dcdf2 B
+  > drop d7a6f907a822 D
+  > pick 591369deedfd X
+  > EOF
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  merging B
+  warning: conflicts while merging B! (edit, then use 'hg resolve --mark')
+  Fix up the change and run hg histedit --continue
+  $ echo b2 > B
+  $ hg resolve --mark B
+  (no more unresolved files)
+  $ hg histedit --continue | fixbundle
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg tglog
+  @  6:03772da75548bb42a8f1eacd8c91d0717a147fcd:draft 'X'
+  |
+  o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+
+base on a previously picked changeset
+  $ echo i > i
+  $ hg add i
+  $ hg commit -m "I"
+  $ echo j > j
+  $ hg add j
+  $ hg commit -m "J"
+  $ hg tglog
+  @  8:e8c55b19d366b335626e805484110d1d5f6f2ea3:draft 'J'
+  |
+  o  7:b2f90fd8aa85db5569e3cfc30cd1d7739546368e:draft 'I'
+  |
+  o  6:03772da75548bb42a8f1eacd8c91d0717a147fcd:draft 'X'
+  |
+  o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  
+  $ hg histedit 5 --commands - 2>&1 << EOF | fixbundle
+  > pick d273e35dcdf2 B
+  > pick 03772da75548 X
+  > base d273e35dcdf2 B
+  > pick e8c55b19d366 J
+  > base d273e35dcdf2 B
+  > pick b2f90fd8aa85 I
+  > EOF
+  abort: may not use "base" with changesets within the edited list
+
+  $ hg --config experimental.histeditng=False histedit 5 --commands - 2>&1 << EOF | fixbundle
+  > base cd010b8cd998 A
+  > pick d273e35dcdf2 B
+  > pick 03772da75548 X
+  > pick b2f90fd8aa85 I
+  > pick e8c55b19d366 J
+  > EOF
+  abort: unknown action "base"
+
+  $ hg tglog
+  @  8:e8c55b19d366b335626e805484110d1d5f6f2ea3:draft 'J'
+  |
+  o  7:b2f90fd8aa85db5569e3cfc30cd1d7739546368e:draft 'I'
+  |
+  o  6:03772da75548bb42a8f1eacd8c91d0717a147fcd:draft 'X'
+  |
+  o  5:d273e35dcdf21a7eb305192ef2e362887cd0a6f8:draft 'B'
+  |
+  | o  4:02de42196ebee42ef284b6780a87cdc96e8eaab6:draft 'H'
+  | |
+  | | o  3:eea13746799a9e0bfd88f29d3c2e9dc9389f524f:draft 'G'
+  | |/|
+  | o |  2:24b6387c8c8cae37178880f3fa95ded3cb1cf785:draft 'F'
+  |/ /
+  | o  1:9520eea781bcca16c1e15acc0ba14335a0e8e5ba:draft 'E'
+  |/
+  o  0:cd010b8cd998f3981a5a8115f94f8da4ab506089:draft 'A'
+  

hgext/histedit.py

@@ -646,6 +646,23 b' class fold(histeditaction):'
             replacements.append((ich, (n,)))
         return repo[n], replacements
 
+class base(histeditaction):
+    def constraints(self):
+        return set(['forceother'])
+
+    def run(self):
+        if self.repo['.'].node() != self.node:
+            mergemod.update(self.repo, self.node, False, True, False)
+            #                                     branchmerge, force, partial)
+        return self.continueclean()
+
+    def continuedirty(self):
+        abortdirty()
+
+    def continueclean(self):
+        basectx = self.repo['.']
+        return basectx, []
+
 class _multifold(fold):
     """fold subclass used for when multiple folds happen in a row
 
@@ -1291,3 +1308,5 b' def extsetup(ui):'
     cmdutil.unfinishedstates.append(
         ['histedit-state', False, True, _('histedit in progress'),
          _("use 'hg histedit --continue' or 'hg histedit --abort'")])
+    if ui.configbool("experimental", "histeditng"):
+        actiontable.update({'b': base, 'base': base})