$ . "$TESTDIR/histedit-helpers.sh"

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > graphlog=
  > histedit=
  > EOF

  $ EDITED="$TESTTMP/editedhistory"
  $ cat > $EDITED <<EOF
  > pick e860deea161a e
  > pick 652413bf663e f
  > fold 177f92b77385 c
  > pick 055a42cdd887 d
  > 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
  > }

  $ initrepo

log before edit
  $ hg log --graph
  @  changeset:   5:652413bf663e
  |  tag:         tip
  |  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
  $ HGEDITOR="cat \"$EDITED\" > " hg histedit 177f92b77385 2>&1 | fixbundle
  0 files updated, 0 files merged, 4 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, 2 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

log after edit
  $ hg log --graph
  @  changeset:   4:82b0c1ff1777
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     d
  |
  o  changeset:   3:150aafb44a91
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     pick e860deea161a e
  |
  o  changeset:   2:493dc0964412
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     e
  |
  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
  

post-fold manifest
  $ hg manifest
  a
  b
  c
  d
  e
  f

  $ cd ..

folding and creating no new change doesn't break:
  $ mkdir fold-to-empty-test
  $ cd fold-to-empty-test
  $ hg init
  $ printf "1\n2\n3\n" > file
  $ hg add file
  $ hg commit -m '1+2+3'
  $ echo 4 >> file
  $ hg commit -m '+4'
  $ echo 5 >> file
  $ hg commit -m '+5'
  $ echo 6 >> file
  $ hg commit -m '+6'
  $ hg log --graph
  @  changeset:   3:251d831eeec5
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     +6
  |
  o  changeset:   2:888f9082bf99
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     +5
  |
  o  changeset:   1:617f94f13c0f
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     +4
  |
  o  changeset:   0:0189ba417d34
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     1+2+3
  

  $ cat > editor.py <<EOF
  > import re, sys
  > rules = sys.argv[1]
  > data = open(rules).read()
  > data = re.sub(r'pick ([0-9a-f]{12} 2 \+5)', r'drop \1', data)
  > data = re.sub(r'pick ([0-9a-f]{12} 2 \+6)', r'fold \1', data)
  > open(rules, 'w').write(data)
  > EOF

  $ HGEDITOR='python editor.py' hg histedit 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  patching file file
  Hunk #1 FAILED at 2
  1 out of 1 hunks FAILED -- saving rejects to file file.rej
  abort: Fix up the change and run hg histedit --continue
  [255]
There were conflicts, but we'll continue without resolving. This
should effectively drop the changes from +6.
  $ hg status
  ? editor.py
  ? file.rej
  $ hg histedit --continue
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/*-backup.hg (glob)
  $ hg log --graph
  @  changeset:   1:617f94f13c0f
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     +4
  |
  o  changeset:   0:0189ba417d34
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     1+2+3
  

  $ cd ..