tests: rework revision branch cache tests

The tests that were added with the revision branch cache in 678f53865c68 had
suffered from bit rot in the development iterations. They were no longer that
"good".

Now, the tests are rewritten and reworked to be more readable and maintainable
and relevant for the actual implementation.

This also utilizes the new 'f' helper tool for keeping an eye the cache files.

tests/test-branches.t

@@ -1,598 +1,623
   $ hg init a
   $ cd a
   $ echo 'root' >root
   $ hg add root
   $ hg commit -d '0 0' -m "Adding root node"
 
   $ echo 'a' >a
   $ hg add a
   $ hg branch a
   marked working directory as branch a
   (branches are permanent and global, did you want a bookmark?)
   $ hg commit -d '1 0' -m "Adding a branch"
 
   $ hg branch q
   marked working directory as branch q
   (branches are permanent and global, did you want a bookmark?)
   $ echo 'aa' >a
   $ hg branch -C
   reset working directory to branch a
   $ hg commit -d '2 0' -m "Adding to a branch"
 
   $ hg update -C 0
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
   $ echo 'b' >b
   $ hg add b
   $ hg branch b
   marked working directory as branch b
   (branches are permanent and global, did you want a bookmark?)
   $ hg commit -d '2 0' -m "Adding b branch"
 
   $ echo 'bh1' >bh1
   $ hg add bh1
   $ hg commit -d '3 0' -m "Adding b branch head 1"
 
   $ hg update -C 2
   1 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ echo 'bh2' >bh2
   $ hg add bh2
   $ hg commit -d '4 0' -m "Adding b branch head 2"
 
   $ echo 'c' >c
   $ hg add c
   $ hg branch c
   marked working directory as branch c
   (branches are permanent and global, did you want a bookmark?)
   $ hg commit -d '5 0' -m "Adding c branch"
 
 reserved names
 
   $ hg branch tip
   abort: the name 'tip' is reserved
   [255]
   $ hg branch null
   abort: the name 'null' is reserved
   [255]
   $ hg branch .
   abort: the name '.' is reserved
   [255]
 
 invalid characters
 
   $ hg branch 'foo:bar'
   abort: ':' cannot be used in a name
   [255]
 
   $ hg branch 'foo
   > bar'
   abort: '\n' cannot be used in a name
   [255]
 
 trailing or leading spaces should be stripped before testing duplicates
 
   $ hg branch 'b '
   abort: a branch of the same name already exists
   (use 'hg update' to switch to it)
   [255]
 
   $ hg branch ' b'
   abort: a branch of the same name already exists
   (use 'hg update' to switch to it)
   [255]
 
 verify update will accept invalid legacy branch names
 
   $ hg init test-invalid-branch-name
   $ cd test-invalid-branch-name
   $ hg pull -u "$TESTDIR"/bundles/test-invalid-branch-name.hg
   pulling from *test-invalid-branch-name.hg (glob)
   requesting all changes
   adding changesets
   adding manifests
   adding file changes
   added 3 changesets with 3 changes to 2 files
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ hg update '"colon:test"'
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd ..
 
   $ echo 'd' >d
   $ hg add d
   $ hg branch 'a branch name much longer than the default justification used by branches'
   marked working directory as branch a branch name much longer than the default justification used by branches
   (branches are permanent and global, did you want a bookmark?)
   $ hg commit -d '6 0' -m "Adding d branch"
 
   $ hg branches
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   b                              4:aee39cd168d0
   c                              6:589736a22561 (inactive)
   a                              5:d8cbc61dbaa6 (inactive)
   default                        0:19709c5a4e75 (inactive)
 
 -------
 
   $ hg branches -a
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   b                              4:aee39cd168d0
 
 --- Branch a
 
   $ hg log -b a
   changeset:   5:d8cbc61dbaa6
   branch:      a
   parent:      2:881fe2b92ad0
   user:        test
   date:        Thu Jan 01 00:00:04 1970 +0000
   summary:     Adding b branch head 2
   
   changeset:   2:881fe2b92ad0
   branch:      a
   user:        test
   date:        Thu Jan 01 00:00:02 1970 +0000
   summary:     Adding to a branch
   
   changeset:   1:dd6b440dd85a
   branch:      a
   user:        test
   date:        Thu Jan 01 00:00:01 1970 +0000
   summary:     Adding a branch
   
 
 ---- Branch b
 
   $ hg log -b b
   changeset:   4:aee39cd168d0
   branch:      b
   user:        test
   date:        Thu Jan 01 00:00:03 1970 +0000
   summary:     Adding b branch head 1
   
   changeset:   3:ac22033332d1
   branch:      b
   parent:      0:19709c5a4e75
   user:        test
   date:        Thu Jan 01 00:00:02 1970 +0000
   summary:     Adding b branch
   
 
 ---- going to test branch closing
 
   $ hg branches
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   b                              4:aee39cd168d0
   c                              6:589736a22561 (inactive)
   a                              5:d8cbc61dbaa6 (inactive)
   default                        0:19709c5a4e75 (inactive)
   $ hg up -C b
   2 files updated, 0 files merged, 4 files removed, 0 files unresolved
   $ echo 'xxx1' >> b
   $ hg commit -d '7 0' -m 'adding cset to branch b'
   $ hg up -C aee39cd168d0
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo 'xxx2' >> b
   $ hg commit -d '8 0' -m 'adding head to branch b'
   created new head
   $ echo 'xxx3' >> b
   $ hg commit -d '9 0' -m 'adding another cset to branch b'
   $ hg branches
   b                             10:bfbe841b666e
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   c                              6:589736a22561 (inactive)
   a                              5:d8cbc61dbaa6 (inactive)
   default                        0:19709c5a4e75 (inactive)
   $ hg heads --closed
   changeset:   10:bfbe841b666e
   branch:      b
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     adding another cset to branch b
   
   changeset:   8:eebb944467c9
   branch:      b
   parent:      4:aee39cd168d0
   user:        test
   date:        Thu Jan 01 00:00:07 1970 +0000
   summary:     adding cset to branch b
   
   changeset:   7:10ff5895aa57
   branch:      a branch name much longer than the default justification used by branches
   user:        test
   date:        Thu Jan 01 00:00:06 1970 +0000
   summary:     Adding d branch
   
   changeset:   6:589736a22561
   branch:      c
   user:        test
   date:        Thu Jan 01 00:00:05 1970 +0000
   summary:     Adding c branch
   
   changeset:   5:d8cbc61dbaa6
   branch:      a
   parent:      2:881fe2b92ad0
   user:        test
   date:        Thu Jan 01 00:00:04 1970 +0000
   summary:     Adding b branch head 2
   
   changeset:   0:19709c5a4e75
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     Adding root node
   
   $ hg heads
   changeset:   10:bfbe841b666e
   branch:      b
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     adding another cset to branch b
   
   changeset:   8:eebb944467c9
   branch:      b
   parent:      4:aee39cd168d0
   user:        test
   date:        Thu Jan 01 00:00:07 1970 +0000
   summary:     adding cset to branch b
   
   changeset:   7:10ff5895aa57
   branch:      a branch name much longer than the default justification used by branches
   user:        test
   date:        Thu Jan 01 00:00:06 1970 +0000
   summary:     Adding d branch
   
   changeset:   6:589736a22561
   branch:      c
   user:        test
   date:        Thu Jan 01 00:00:05 1970 +0000
   summary:     Adding c branch
   
   changeset:   5:d8cbc61dbaa6
   branch:      a
   parent:      2:881fe2b92ad0
   user:        test
   date:        Thu Jan 01 00:00:04 1970 +0000
   summary:     Adding b branch head 2
   
   changeset:   0:19709c5a4e75
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     Adding root node
   
   $ hg commit -d '9 0' --close-branch -m 'prune bad branch'
   $ hg branches -a
   b                              8:eebb944467c9
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   $ hg up -C b
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg commit -d '9 0' --close-branch -m 'close this part branch too'
   $ hg commit -d '9 0' --close-branch -m 're-closing this branch'
   abort: can only close branch heads
   [255]
 
   $ hg log -r tip --debug
   changeset:   12:e3d49c0575d8fc2cb1cd6859c747c14f5f6d499f
   branch:      b
   tag:         tip
   phase:       draft
   parent:      8:eebb944467c9fb9651ed232aeaf31b3c0a7fc6c1
   parent:      -1:0000000000000000000000000000000000000000
   manifest:    8:6f9ed32d2b310e391a4f107d5f0f071df785bfee
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   extra:       branch=b
   extra:       close=1
   description:
   close this part branch too
   
   
 --- b branch should be inactive
 
   $ hg branches
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   c                              6:589736a22561 (inactive)
   a                              5:d8cbc61dbaa6 (inactive)
   default                        0:19709c5a4e75 (inactive)
   $ hg branches -c
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   b                             12:e3d49c0575d8 (closed)
   c                              6:589736a22561 (inactive)
   a                              5:d8cbc61dbaa6 (inactive)
   default                        0:19709c5a4e75 (inactive)
   $ hg branches -a
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
   $ hg branches -q
   a branch name much longer than the default justification used by branches
   c
   a
   default
   $ hg heads b
   no open branch heads found on branches b
   [1]
   $ hg heads --closed b
   changeset:   12:e3d49c0575d8
   branch:      b
   tag:         tip
   parent:      8:eebb944467c9
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     close this part branch too
   
   changeset:   11:d3f163457ebf
   branch:      b
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     prune bad branch
   
   $ echo 'xxx4' >> b
   $ hg commit -d '9 0' -m 'reopen branch with a change'
   reopening closed branch head 12
 
 --- branch b is back in action
 
   $ hg branches -a
   b                             13:e23b5505d1ad
   a branch name much longer than the default justification used by branches 7:10ff5895aa57
 
 ---- test heads listings
 
   $ hg heads
   changeset:   13:e23b5505d1ad
   branch:      b
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     reopen branch with a change
   
   changeset:   7:10ff5895aa57
   branch:      a branch name much longer than the default justification used by branches
   user:        test
   date:        Thu Jan 01 00:00:06 1970 +0000
   summary:     Adding d branch
   
   changeset:   6:589736a22561
   branch:      c
   user:        test
   date:        Thu Jan 01 00:00:05 1970 +0000
   summary:     Adding c branch
   
   changeset:   5:d8cbc61dbaa6
   branch:      a
   parent:      2:881fe2b92ad0
   user:        test
   date:        Thu Jan 01 00:00:04 1970 +0000
   summary:     Adding b branch head 2
   
   changeset:   0:19709c5a4e75
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     Adding root node
   
 
 branch default
 
   $ hg heads default
   changeset:   0:19709c5a4e75
   user:        test
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     Adding root node
   
 
 branch a
 
   $ hg heads a
   changeset:   5:d8cbc61dbaa6
   branch:      a
   parent:      2:881fe2b92ad0
   user:        test
   date:        Thu Jan 01 00:00:04 1970 +0000
   summary:     Adding b branch head 2
   
   $ hg heads --active a
   no open branch heads found on branches a
   [1]
 
 branch b
 
   $ hg heads b
   changeset:   13:e23b5505d1ad
   branch:      b
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     reopen branch with a change
   
   $ hg heads --closed b
   changeset:   13:e23b5505d1ad
   branch:      b
   tag:         tip
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     reopen branch with a change
   
   changeset:   11:d3f163457ebf
   branch:      b
   user:        test
   date:        Thu Jan 01 00:00:09 1970 +0000
   summary:     prune bad branch
   
 default branch colors:
 
   $ cat <<EOF >> $HGRCPATH
   > [extensions]
   > color =
   > [color]
   > mode = ansi
   > EOF
 
   $ hg up -C c
   3 files updated, 0 files merged, 2 files removed, 0 files unresolved
   $ hg commit -d '9 0' --close-branch -m 'reclosing this branch'
   $ hg up -C b
   2 files updated, 0 files merged, 3 files removed, 0 files unresolved
   $ hg branches --color=always
   \x1b[0;32mb\x1b[0m\x1b[0;33m                             13:e23b5505d1ad\x1b[0m (esc)
   \x1b[0;0ma branch name much longer than the default justification used by branches\x1b[0m\x1b[0;33m 7:10ff5895aa57\x1b[0m (esc)
   \x1b[0;0ma\x1b[0m\x1b[0;33m                              5:d8cbc61dbaa6\x1b[0m (inactive) (esc)
   \x1b[0;0mdefault\x1b[0m\x1b[0;33m                        0:19709c5a4e75\x1b[0m (inactive) (esc)
 
 default closed branch color:
 
   $ hg branches --color=always --closed
   \x1b[0;32mb\x1b[0m\x1b[0;33m                             13:e23b5505d1ad\x1b[0m (esc)
   \x1b[0;0ma branch name much longer than the default justification used by branches\x1b[0m\x1b[0;33m 7:10ff5895aa57\x1b[0m (esc)
   \x1b[0;30;1mc\x1b[0m\x1b[0;33m                             14:f894c25619d3\x1b[0m (closed) (esc)
   \x1b[0;0ma\x1b[0m\x1b[0;33m                              5:d8cbc61dbaa6\x1b[0m (inactive) (esc)
   \x1b[0;0mdefault\x1b[0m\x1b[0;33m                        0:19709c5a4e75\x1b[0m (inactive) (esc)
 
   $ cat <<EOF >> $HGRCPATH
   > [extensions]
   > color =
   > [color]
   > branches.active = green
   > branches.closed = blue
   > branches.current = red
   > branches.inactive = magenta
   > log.changeset = cyan
   > EOF
 
 custom branch colors:
 
   $ hg branches --color=always
   \x1b[0;31mb\x1b[0m\x1b[0;36m                             13:e23b5505d1ad\x1b[0m (esc)
   \x1b[0;32ma branch name much longer than the default justification used by branches\x1b[0m\x1b[0;36m 7:10ff5895aa57\x1b[0m (esc)
   \x1b[0;35ma\x1b[0m\x1b[0;36m                              5:d8cbc61dbaa6\x1b[0m (inactive) (esc)
   \x1b[0;35mdefault\x1b[0m\x1b[0;36m                        0:19709c5a4e75\x1b[0m (inactive) (esc)
 
 custom closed branch color:
 
   $ hg branches --color=always --closed
   \x1b[0;31mb\x1b[0m\x1b[0;36m                             13:e23b5505d1ad\x1b[0m (esc)
   \x1b[0;32ma branch name much longer than the default justification used by branches\x1b[0m\x1b[0;36m 7:10ff5895aa57\x1b[0m (esc)
   \x1b[0;34mc\x1b[0m\x1b[0;36m                             14:f894c25619d3\x1b[0m (closed) (esc)
   \x1b[0;35ma\x1b[0m\x1b[0;36m                              5:d8cbc61dbaa6\x1b[0m (inactive) (esc)
   \x1b[0;35mdefault\x1b[0m\x1b[0;36m                        0:19709c5a4e75\x1b[0m (inactive) (esc)
 
 template output:
 
   $ hg branches -Tjson --closed
   [
    {
     "active": true,
     "branch": "b",
     "closed": false,
     "current": true,
     "node": "e23b5505d1ad24aab6f84fd8c7cb8cd8e5e93be0",
     "rev": 13
    },
    {
     "active": true,
     "branch": "a branch name much longer than the default justification used by branches",
     "closed": false,
     "current": false,
     "node": "10ff5895aa5793bd378da574af8cec8ea408d831",
     "rev": 7
    },
    {
     "active": false,
     "branch": "c",
     "closed": true,
     "current": false,
     "node": "f894c25619d3f1484639d81be950e0a07bc6f1f6",
     "rev": 14
    },
    {
     "active": false,
     "branch": "a",
     "closed": false,
     "current": false,
     "node": "d8cbc61dbaa6dc817175d1e301eecb863f280832",
     "rev": 5
    },
    {
     "active": false,
     "branch": "default",
     "closed": false,
     "current": false,
     "node": "19709c5a4e75bf938f8e349aff97438539bb729e",
     "rev": 0
    }
   ]
 
-revision branch name caching implementation
+
+Tests of revision branch name caching
+
+We rev branch cache is updated automatically. In these tests we use a trick to
+trigger rebuilds. We remove the branch head cache and run 'hg head' to cause a
+rebuild that also will populate the rev branch cache.
 
-cache creation
-  $ rm .hg/cache/rbc-revs-v1
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-  $ [ -f .hg/cache/rbc-revs-v1 ] || echo no file
-  no file
-recovery from invalid cache file
-  $ echo > .hg/cache/rbc-revs-v1
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-cache update NOT fully written from revset
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  68b329da9893e34099c7d8ad5cb9c940  .hg/cache/rbc-revs-v1
-recovery from other corruption - extra trailing data
+revision branch cache is created when building the branch head cache
+  $ rm -rf .hg/cache; hg head a -T '{rev}\n'
+  5
+  $ f --hexdump --size .hg/cache/rbc-*
+  .hg/cache/rbc-names-v1: size=87
+  0000: 64 65 66 61 75 6c 74 00 61 00 62 00 63 00 61 20 |default.a.b.c.a |
+  0010: 62 72 61 6e 63 68 20 6e 61 6d 65 20 6d 75 63 68 |branch name much|
+  0020: 20 6c 6f 6e 67 65 72 20 74 68 61 6e 20 74 68 65 | longer than the|
+  0030: 20 64 65 66 61 75 6c 74 20 6a 75 73 74 69 66 69 | default justifi|
+  0040: 63 61 74 69 6f 6e 20 75 73 65 64 20 62 79 20 62 |cation used by b|
+  0050: 72 61 6e 63 68 65 73                            |ranches|
+  .hg/cache/rbc-revs-v1: size=120
+  0000: 19 70 9c 5a 00 00 00 00 dd 6b 44 0d 00 00 00 01 |.p.Z.....kD.....|
+  0010: 88 1f e2 b9 00 00 00 01 ac 22 03 33 00 00 00 02 |.........".3....|
+  0020: ae e3 9c d1 00 00 00 02 d8 cb c6 1d 00 00 00 01 |................|
+  0030: 58 97 36 a2 00 00 00 03 10 ff 58 95 00 00 00 04 |X.6.......X.....|
+  0040: ee bb 94 44 00 00 00 02 5f 40 61 bb 00 00 00 02 |...D...._@a.....|
+  0050: bf be 84 1b 00 00 00 02 d3 f1 63 45 80 00 00 02 |..........cE....|
+  0060: e3 d4 9c 05 80 00 00 02 e2 3b 55 05 00 00 00 02 |.........;U.....|
+  0070: f8 94 c2 56 80 00 00 03                         |...V....|
+recovery from invalid cache revs file with trailing data
   $ echo >> .hg/cache/rbc-revs-v1
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-cache update NOT fully written from revset
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  e1c06d85ae7b8b032bef47e42e4c08f9  .hg/cache/rbc-revs-v1
-lazy update after commit
-  $ hg tag tag
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  d0c0166808ee0a1f0e8894915ad363b6  .hg/cache/rbc-revs-v1
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  d0c0166808ee0a1f0e8894915ad363b6  .hg/cache/rbc-revs-v1
-update after rollback - cache keeps stripped revs until written for other reasons
+  $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=120
+recovery from invalid cache file with partial last record
+  $ mv .hg/cache/rbc-revs-v1 .
+  $ f -qDB 119 rbc-revs-v1 > .hg/cache/rbc-revs-v1
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=119
+  $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=120
+recovery from invalid cache file with missing record - no truncation
+  $ mv .hg/cache/rbc-revs-v1 .
+  $ f -qDB 112 rbc-revs-v1 > .hg/cache/rbc-revs-v1
+  $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=120
+recovery from invalid cache file with some bad records
+  $ mv .hg/cache/rbc-revs-v1 .
+  $ f -qDB 8 rbc-revs-v1 > .hg/cache/rbc-revs-v1
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=8
+  $ f -qDB 112 rbc-revs-v1 >> .hg/cache/rbc-revs-v1
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=120
+  $ hg log -r 'branch(.)' -T '{rev} '
+  3 4 8 9 10 11 12 13  (no-eol)
+  $ rm -f .hg/cache/branch* && hg head a -T '{rev}\n' --debug
+  5
+  $ f --size --hexdump --bytes=16 .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=120
+  0000: 19 70 9c 5a 00 00 00 00 dd 6b 44 0d 00 00 00 01 |.p.Z.....kD.....|
+cache is updated when committing
+  $ hg branch i-will-regret-this
+  marked working directory as branch i-will-regret-this
+  (branches are permanent and global, did you want a bookmark?)
+  $ hg ci -m regrets
+  $ f --size .hg/cache/rbc-*
+  .hg/cache/rbc-names-v1: size=106
+  .hg/cache/rbc-revs-v1: size=128
+update after rollback - the cache will be correct but rbc-names will will still
+contain the branch name even though it no longer is used
   $ hg up -qr '.^'
   $ hg rollback -qf
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  d8c2acdc229bf942fde1dfdbe8f9d933  .hg/cache/rbc-revs-v1
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  d8c2acdc229bf942fde1dfdbe8f9d933  .hg/cache/rbc-revs-v1
-handle history mutations that doesn't change the tip node - this is a problem
-with the cache invalidation scheme used by branchmap
-  $ hg log -r tip+b -T'{rev}:{node|short} {branch}\n'
-  14:f894c25619d3 c
-  13:e23b5505d1ad b
-  $ hg bundle -q --all bu.hg
-  $ hg --config extensions.strip= strip --no-b -qr -1:
-  $ hg up -q tip
-  $ hg branch
-  b
-  $ hg branch -q hacked
-  $ hg ci --amend -qm 'hacked'
-  $ hg pull -q bu.hg -r f894c25619d3
-  $ hg log -r tip+b -T'{rev}:{node|short} {branch}\n'
-  14:f894c25619d3 c
-  12:e3d49c0575d8 b
-  $ hg debugrevspec 'branch("hacked")'
-  13
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  22424d7e106c894336d9d705b0241bc5  .hg/cache/rbc-revs-v1
-cleanup, restore old state
-  $ hg --config extensions.strip= strip --no-b -qr -2:
-  $ hg pull -q bu.hg
-  $ rm bu.hg
-  $ hg up -qr tip
-  $ hg log -r tip -T'{rev}:{node|short}\n'
-  14:f894c25619d3
-the cache file do not go back to the old state - it still contains the
-now unused 'hacked' branch name)
-  $ hg debugrevspec 'branch("re:a ")'
-  7
-  $ "$TESTDIR/md5sum.py" .hg/cache/rbc-revs-v1
-  d8c2acdc229bf942fde1dfdbe8f9d933  .hg/cache/rbc-revs-v1
-  $ cat .hg/cache/rbc-names-v1
-  default\x00a\x00b\x00c\x00a branch name much longer than the default justification used by branches\x00hacked (no-eol) (esc)
+  $ f --size --hexdump .hg/cache/rbc-*
+  .hg/cache/rbc-names-v1: size=106
+  0000: 64 65 66 61 75 6c 74 00 61 00 62 00 63 00 61 20 |default.a.b.c.a |
+  0010: 62 72 61 6e 63 68 20 6e 61 6d 65 20 6d 75 63 68 |branch name much|
+  0020: 20 6c 6f 6e 67 65 72 20 74 68 61 6e 20 74 68 65 | longer than the|
+  0030: 20 64 65 66 61 75 6c 74 20 6a 75 73 74 69 66 69 | default justifi|
+  0040: 63 61 74 69 6f 6e 20 75 73 65 64 20 62 79 20 62 |cation used by b|
+  0050: 72 61 6e 63 68 65 73 00 69 2d 77 69 6c 6c 2d 72 |ranches.i-will-r|
+  0060: 65 67 72 65 74 2d 74 68 69 73                   |egret-this|
+  .hg/cache/rbc-revs-v1: size=120
+  0000: 19 70 9c 5a 00 00 00 00 dd 6b 44 0d 00 00 00 01 |.p.Z.....kD.....|
+  0010: 88 1f e2 b9 00 00 00 01 ac 22 03 33 00 00 00 02 |.........".3....|
+  0020: ae e3 9c d1 00 00 00 02 d8 cb c6 1d 00 00 00 01 |................|
+  0030: 58 97 36 a2 00 00 00 03 10 ff 58 95 00 00 00 04 |X.6.......X.....|
+  0040: ee bb 94 44 00 00 00 02 5f 40 61 bb 00 00 00 02 |...D...._@a.....|
+  0050: bf be 84 1b 00 00 00 02 d3 f1 63 45 80 00 00 02 |..........cE....|
+  0060: e3 d4 9c 05 80 00 00 02 e2 3b 55 05 00 00 00 02 |.........;U.....|
+  0070: f8 94 c2 56 80 00 00 03                         |...V....|
+cache is updated/truncated when stripping - it is thus very hard to get in a
+situation where the cache is out of sync and the hash check detects it
+  $ hg --config extensions.strip= strip -r tip --nob
+  $ f --size .hg/cache/rbc-revs*
+  .hg/cache/rbc-revs-v1: size=112
 
   $ cd ..