histedit: demonstrate breakage when `update` to a revision breaks

I'm honestly impressed that nobody has hit this in the over a decade
that histedit has existed, but here we are.

Differential Revision: https://phab.mercurial-scm.org/D6881

tests/test-histedit-non-commute-abort.t

@@ -1,165 +1,216 b''
   $ . "$TESTDIR/histedit-helpers.sh"
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > histedit=
   > EOF
 
   $ initrepo ()
   > {
   >     hg init r
   >     cd r
   >     for x in a b c d e f ; do
   >         echo $x > $x
   >         hg add $x
   >         hg ci -m $x
   >     done
   >     echo a >> e
   >     hg ci -m 'does not commute with e'
   >     cd ..
   > }
 
   $ initrepo
   $ cd r
 
 log before edit
   $ hg log --graph
   @  changeset:   6:bfa474341cc9
   |  tag:         tip
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     does not commute with e
   |
   o  changeset:   5:652413bf663e
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     f
   |
   o  changeset:   4:e860deea161a
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     e
   |
   o  changeset:   3:055a42cdd887
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     d
   |
   o  changeset:   2:177f92b77385
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     c
   |
   o  changeset:   1:d2ae7f538514
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     b
   |
   o  changeset:   0:cb9a9f314b8b
      user:        test
      date:        Thu Jan 01 00:00:00 1970 +0000
      summary:     a
   
 
 edit the history
   $ hg histedit 177f92b77385 --commands - 2>&1 <<EOF | fixbundle
   > pick 177f92b77385 c
   > pick 055a42cdd887 d
   > pick bfa474341cc9 does not commute with e
   > pick e860deea161a e
   > pick 652413bf663e f
   > EOF
   merging e
   warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
   Fix up the change (pick e860deea161a)
   (hg histedit --continue to resume)
 
 insert unsupported advisory merge record
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -x
   $ hg debugmergestate
   * version 2 records
   local: 8f7551c7e4a2f2efe0bc8c741baf7f227d65d758
   other: e860deea161a2f77de56603b340ebbb4536308ae
   labels:
     local: local
     other: histedit
   unrecognized entry: x	advisory record
   file extras: e (ancestorlinknode = 0000000000000000000000000000000000000000)
   file: e (record type "F", state "u", hash 58e6b3a414a1e090dfc6029add0f3555ccba127f)
     local path: e (flags "")
     ancestor path: e (node null)
     other path: e (node 6b67ccefd5ce6de77e7ead4f5292843a0255329f)
   $ hg resolve -l
   U e
 
 insert unsupported mandatory merge record
   $ hg --config extensions.fakemergerecord=$TESTDIR/fakemergerecord.py fakemergerecord -X
   $ hg debugmergestate
   * version 2 records
   local: 8f7551c7e4a2f2efe0bc8c741baf7f227d65d758
   other: e860deea161a2f77de56603b340ebbb4536308ae
   labels:
     local: local
     other: histedit
   file extras: e (ancestorlinknode = 0000000000000000000000000000000000000000)
   file: e (record type "F", state "u", hash 58e6b3a414a1e090dfc6029add0f3555ccba127f)
     local path: e (flags "")
     ancestor path: e (node null)
     other path: e (node 6b67ccefd5ce6de77e7ead4f5292843a0255329f)
   unrecognized entry: X	mandatory record
   $ hg resolve -l
   abort: unsupported merge state records: X
   (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
   [255]
   $ hg resolve -ma
   abort: unsupported merge state records: X
   (see https://mercurial-scm.org/wiki/MergeStateRecords for more information)
   [255]
 
 abort the edit (should clear out merge state)
   $ hg histedit --abort 2>&1 | fixbundle
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg debugmergestate
   no merge state found
 
 log after abort
   $ hg resolve -l
   $ hg log --graph
   @  changeset:   6:bfa474341cc9
   |  tag:         tip
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     does not commute with e
   |
   o  changeset:   5:652413bf663e
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     f
   |
   o  changeset:   4:e860deea161a
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     e
   |
   o  changeset:   3:055a42cdd887
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     d
   |
   o  changeset:   2:177f92b77385
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     c
   |
   o  changeset:   1:d2ae7f538514
   |  user:        test
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     b
   |
   o  changeset:   0:cb9a9f314b8b
      user:        test
      date:        Thu Jan 01 00:00:00 1970 +0000
      summary:     a
   
 
+Early tree conflict doesn't leave histedit in a wedged state.
+  $ hg rm c
+  $ hg ci -m 'remove c'
+  $ echo collision > c
+
+  $ hg histedit e860deea161a --commands - 2>&1 <<EOF
+  > edit e860deea161a
+  > pick 652413bf663e
+  > pick bfa474341cc9
+  > pick 1b0954ff00fc
+  > EOF
+  c: untracked file differs
+  abort: untracked files in working directory differ from files in requested revision
+  [255]
+
+BUG: we didn't actually change p1 of the working copy, but we're in a
+histedit state. This confuses the process very badly and leads to
+histedit stripping things it shouldn't (in obsmarker mode it inserts
+bogus prune markers in this case.)
+
+  $ hg log -r 'p1()' -T'{node}\n'
+  1b0954ff00fccb15a37b679e4a35e9b01dfe685e
+  $ hg status --config ui.tweakdefaults=yes
+  ? c
+  ? e.orig
+  # The repository is in an unfinished *histedit* state.
+  
+  # To continue:    hg histedit --continue
+  # To abort:       hg histedit --abort
+  
+  $ hg histedit --continue
+  652413bf663e: skipping changeset (no changes)
+  bfa474341cc9: skipping changeset (no changes)
+  1b0954ff00fc: skipping changeset (no changes)
+  saved backup bundle to $TESTTMP/r/.hg/strip-backup/e860deea161a-a0738322-histedit.hg
+
+  $ hg log -GTcompact
+  warning: ignoring unknown working parent 1b0954ff00fc!
+  o  3[tip]   055a42cdd887   1970-01-01 00:00 +0000   test
+  |    d
+  |
+  o  2   177f92b77385   1970-01-01 00:00 +0000   test
+  |    c
+  |
+  o  1   d2ae7f538514   1970-01-01 00:00 +0000   test
+  |    b
+  |
+  o  0   cb9a9f314b8b   1970-01-01 00:00 +0000   test
+       a
+  
+
   $ cd ..