tests/test-histedit-no-backup.t

rust: simplify pattern file parsing

Previously we kept the pattern syntax as a &[u8] until the last
possible moment, which meant we had to handle potential errors when
parsing that &[u8].  But such errors could never actually occur, given
the structure of the code.

Now we parse it eagerly (in two places) and pass it around as a
PatternSyntax, so we can delete some error handling code.

parse_one_pattern is in particular useful for parsing patterns passed
on the command line, as we'll support later in this series.

#testcases abortcommand abortflag

#if abortflag
  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > abort = histedit --abort
  > EOF
#endif

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

Enable extension used by this test
  $ cat >>$HGRCPATH <<EOF
  > [extensions]
  > histedit=
  > EOF

=================================
Test backup-bundle config option|
=================================
Repo setup:
  $ hg init foo
  $ cd foo
  $ echo first>file
  $ hg ci -qAm one
  $ echo second>>file
  $ hg ci -m two
  $ echo third>>file
  $ hg ci -m three
  $ echo forth>>file
  $ hg ci -m four
  $ hg log -G --style compact
  @  3[tip]   7d5187087c79   1970-01-01 00:00 +0000   test
  |    four
  |
  o  2   80d23dfa866d   1970-01-01 00:00 +0000   test
  |    three
  |
  o  1   6153eb23e623   1970-01-01 00:00 +0000   test
  |    two
  |
  o  0   36b4bdd91f5b   1970-01-01 00:00 +0000   test
       one
  
Test when `backup-bundle` config option is enabled:
  $ hg histedit -r '36b4bdd91f5b' --commands - << EOF
  > pick 36b4bdd91f5b 0 one
  > pick 6153eb23e623 1 two
  > roll 80d23dfa866d 2 three
  > edit 7d5187087c79 3 four
  > EOF
  merging file
  Editing (7d5187087c79), commit as needed now to split the change
  (to edit 7d5187087c79, `hg histedit --continue` after making changes)
  [240]
  $ hg abort
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/foo/.hg/strip-backup/1d8f701c7b35-cf7be322-backup.hg
  saved backup bundle to $TESTTMP/foo/.hg/strip-backup/5c0056670bce-b54b65d0-backup.hg

Test when `backup-bundle` config option is not enabled
Enable config option:
  $ cat >>$HGRCPATH <<EOF
  > [rewrite]
  > backup-bundle = False
  > EOF

  $ hg histedit -r '36b4bdd91f5b' --commands - << EOF
  > pick 36b4bdd91f5b 0 one
  > pick 6153eb23e623 1 two
  > roll 80d23dfa866d 2 three
  > edit 7d5187087c79 3 four
  > EOF
  merging file
  Editing (7d5187087c79), commit as needed now to split the change
  (to edit 7d5187087c79, `hg histedit --continue` after making changes)
  [240]

  $ hg abort
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved