tests/test-histedit-no-backup.t

revisions: allow "x123" to refer to nodeid prefix "123"

When resolving "123" to a revision, we try to interpret it as revnum
before we try to interpret it as a nodeid hex prefix. This can lead to
the shortest valid prefix being longer than necessary. This patch lets
us write such nodeids in a shorter form by prefixing them with "x"
instead of adding more hex digits until they're longer than the
longest decimal revnum.

On my hg repo with almost 69k revisions, turning this feature on saves
on average 0.4% on the average nodeid length. That clearly doesn't
justify this patch. However, it becomes more usefule when combined
with the earlier patches in this series that let you disambiguate
nodeid prefixes within a configured revset.

Note that we attempt to resolve symbols as nodeid prefixes after we've
exhausted all other posibilities, so this is a backwards compatible
change (only queries that would previously fail may now succeed).

I've still hidden this feature behind an experiemntal config option so
we can roll it back if needed.

Differential Revision: https://phab.mercurial-scm.org/D4041

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

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

==========================================
Test history-editing-backup 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 `history-editing-backup` 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), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [1]
  $ hg histedit --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 `history-editing-backup` config option is not enabled
Enable config option:
  $ cat >>$HGRCPATH <<EOF
  > [ui]
  > history-editing-backup=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), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [1]
  $ hg histedit --abort
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved