$ branchcache=.hg/cache/branch2

  $ listbranchcaches() {
  >    for f in .hg/cache/branch2*;
  >       do echo === $f ===;
  >       cat $f;
  >     done;
  > }
  $ purgebranchcaches() {
  >     rm .hg/cache/branch2*
  > }

  $ hg init t
  $ cd t

  $ hg branches
  $ echo foo > a
  $ hg add a
  $ hg ci -m "initial"
  $ hg branch foo
  marked working directory as branch foo
  (branches are permanent and global, did you want a bookmark?)
  $ hg branch
  foo
  $ hg ci -m "add branch name"
  $ hg branch bar
  marked working directory as branch bar
  $ hg ci -m "change branch name"

Branch shadowing:

  $ hg branch default
  abort: a branch of the same name already exists
  (use 'hg update' to switch to it)
  [10]

  $ hg branch -f default
  marked working directory as branch default

  $ hg ci -m "clear branch name"
  created new head

There should be only one default branch head

  $ hg heads .
  changeset:   3:1c28f494dae6
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     clear branch name
  
Merging and branches

  $ hg co foo
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch
  foo

 set existing branch name fails unless force - setting existing parent branch works without force:

  $ hg branch bar
  abort: a branch of the same name already exists
  (use 'hg update' to switch to it)
  [10]

  $ hg branch -f bar
  marked working directory as branch bar

  $ hg branch foo
  marked working directory as branch foo

  $ echo bleah > a
  $ hg ci -m "modify a branch"

  $ hg merge default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg branch
  foo

 set existing branch name where branch head is ancestor:

  $ hg branch bar
  abort: a branch of the same name already exists
  (use 'hg update' to switch to it)
  [10]

 set (other) parent branch as branch name

  $ hg branch default
  marked working directory as branch default

 set (first) parent branch as branch name

  $ hg branch foo
  marked working directory as branch foo

  $ hg ci -m "merge"

  $ hg log -G -T '{rev}:{node|short} {branch} {desc}\n'
  @    5:530046499edf foo merge
  |\
  | o  4:adf1a74a7f7b foo modify a branch
  | |
  o |  3:1c28f494dae6 default clear branch name
  | |
  o |  2:c21617b13b22 bar change branch name
  |/
  o  1:6c0e42da283a foo add branch name
  |
  o  0:db01e8ea3388 default initial
  
  $ hg branches
  foo                            5:530046499edf
  default                        3:1c28f494dae6 (inactive)
  bar                            2:c21617b13b22 (inactive)

  $ hg branches -q
  foo
  default
  bar

Test for invalid branch cache:

  $ hg rollback
  repository tip rolled back to revision 4 (undo commit)
  working directory now based on revisions 4 and 3

  $ cp ${branchcache}-served .hg/bc-invalid

  $ hg log -r foo
  changeset:   4:adf1a74a7f7b
  branch:      foo
  tag:         tip
  parent:      1:6c0e42da283a
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     modify a branch
  
  $ cp .hg/bc-invalid $branchcache

  $ hg --debug log -r foo
  changeset:   4:adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6
  branch:      foo
  tag:         tip
  phase:       draft
  parent:      1:6c0e42da283a56b5edc5b4fadb491365ec7f5fa8
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    1:8c342a37dfba0b3d3ce073562a00d8a813c54ffe
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files:       a
  extra:       branch=foo
  description:
  modify a branch
  
  
  $ purgebranchcaches
  $ echo corrupted > $branchcache

  $ hg log -qr foo
  4:adf1a74a7f7b

  $ listbranchcaches
  === .hg/cache/branch2 ===
  corrupted
  === .hg/cache/branch2-served ===
  adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4
  c21617b13b220988e7a2e26290fbe4325ffa7139 o bar
  1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default
  adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo

Push should update the branch cache:

  $ hg init ../target

Pushing just rev 0:

  $ hg push -qr 0 ../target

  $ (cd ../target/; listbranchcaches)
  === .hg/cache/branch2-base ===
  db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 0
  db01e8ea3388fd3c7c94e1436ea2bd6a53d581c5 o default

Pushing everything:

  $ hg push -qf ../target

  $ (cd ../target/; listbranchcaches)
  === .hg/cache/branch2-base ===
  adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 4
  c21617b13b220988e7a2e26290fbe4325ffa7139 o bar
  1c28f494dae69a2f8fc815059d257eccf3fcfe75 o default
  adf1a74a7f7b4cd193d12992f5d0d6a004ed21d6 o foo

Update with no arguments: tipmost revision of the current branch:

  $ hg up -q -C 0
  $ hg up -q
  $ hg id
  1c28f494dae6

  $ hg up -q 1
  $ hg up -q
  $ hg id
  adf1a74a7f7b (foo) tip

  $ hg branch foobar
  marked working directory as branch foobar

  $ hg up
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

Fast-forward merge:

  $ hg branch ff
  marked working directory as branch ff

  $ echo ff > ff
  $ hg ci -Am'fast forward'
  adding ff

  $ hg up foo
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ hg merge ff
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg branch
  foo
  $ hg commit -m'Merge ff into foo'
  $ hg parents
  changeset:   6:185ffbfefa30
  branch:      foo
  tag:         tip
  parent:      4:adf1a74a7f7b
  parent:      5:1a3c27dc5e11
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     Merge ff into foo
  
  $ hg manifest
  a
  ff


Test merging, add 3 default heads and one test head:

  $ cd ..
  $ hg init merges
  $ cd merges
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ echo b > b
  $ hg ci -Amb
  adding b

  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo c > c
  $ hg ci -Amc
  adding c
  created new head

  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo d > d
  $ hg ci -Amd
  adding d
  created new head

  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch test
  marked working directory as branch test
  (branches are permanent and global, did you want a bookmark?)
  $ echo e >> e
  $ hg ci -Ame
  adding e

  $ hg log
  changeset:   4:3a1e01ed1df4
  branch:      test
  tag:         tip
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     e
  
  changeset:   3:980f7dc84c29
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     d
  
  changeset:   2:d36c0562f908
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
  changeset:   1:d2ae7f538514
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  changeset:   0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
Implicit merge with test branch as parent:

  $ hg merge
  abort: branch 'test' has one head - please merge with an explicit rev
  (run 'hg heads' to see all heads, specify rev with -r)
  [255]
  $ hg up -C default
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

Implicit merge with default branch as parent:

  $ hg merge
  abort: branch 'default' has 3 heads - please merge with an explicit rev
  (run 'hg heads .' to see heads, specify rev with -r)
  [255]

3 branch heads, explicit merge required:

  $ hg merge 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m merge

2 branch heads, implicit merge works:

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cd ..

We expect that bare update on new branch, updates to parent

  $ hg init bareupdateonnewbranch
  $ cd bareupdateonnewbranch
  $ hg update
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ touch a
  $ hg commit -A -m "a"
  adding a
  $ touch b
  $ hg commit -A -m "b"
  adding b
  $ touch c
  $ hg commit -A -m "c"
  adding c
  $ hg update -r 1
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg log -G
  o  changeset:   2:991a3460af53
  |  tag:         tip
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     c
  |
  @  changeset:   1:0e067c57feba
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     b
  |
  o  changeset:   0:3903775176ed
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     a
  
  $ hg branch dev
  marked working directory as branch dev
  (branches are permanent and global, did you want a bookmark?)
  $ hg update
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg summary
  parent: 1:0e067c57feba 
   b
  branch: dev
  commit: (new branch)
  update: (current)
  phases: 3 draft

  $ cd ..

We need special handling for repositories with no "default" branch because
"null" revision belongs to non-existent "default" branch.

  $ hg init nodefault
  $ cd nodefault
  $ hg branch -q foo
  $ touch 0
  $ hg ci -Aqm0
  $ touch 1
  $ hg ci -Aqm1
  $ hg update -qr0
  $ hg branch -q bar
  $ touch 2
  $ hg ci -Aqm2
  $ hg update -qr0
  $ hg branch -q baz
  $ touch 3
  $ hg ci -Aqm3
  $ hg ci --close-branch -m 'close baz'
  $ hg update -q null
  $ hg log -GT'{rev} {branch}\n'
  _  4 baz
  |
  o  3 baz
  |
  | o  2 bar
  |/
  | o  1 foo
  |/
  o  0 foo
  

 a) updating from "null" should bring us to the tip-most branch head as
 there is no "default" branch:

  $ hg update -q null
  $ hg id -bn
  -1 default
  $ hg update
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id -bn
  2 bar

 b) but if we are at uncommitted "default" branch, we should stick to the
 current revision:

  $ hg update -q 0
  $ hg branch default
  marked working directory as branch default
  $ hg id -bn
  0 default
  $ hg update
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id -bn
  0 default

 c) also, if we have uncommitted branch at "null", we should stick to it:

  $ hg update -q null
  $ hg branch new
  marked working directory as branch new
  $ hg id -bn
  -1 new
  $ hg update
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg id -bn
  -1 new

  $ cd ..

We expect that update --clean discard changes in working directory,
and updates to the head of parent branch.

  $ hg init updatebareclean
  $ cd updatebareclean
  $ hg update --clean
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ touch a
  $ hg commit -A -m "a"
  adding a
  $ touch b
  $ hg commit -A -m "b"
  adding b
  $ touch c
  $ hg commit -A -m "c"
  adding c
  $ hg log
  changeset:   2:991a3460af53
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
  changeset:   1:0e067c57feba
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  changeset:   0:3903775176ed
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     a
  
  $ hg update -r 1
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch new-branch
  marked working directory as branch new-branch
  (branches are permanent and global, did you want a bookmark?)
  $ echo "aa" >> a
  $ hg update --clean
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg status
  $ hg branch
  default
  $ hg parent
  changeset:   2:991a3460af53
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
We expect that update --clean on non existing parent discards a new branch
and updates to the tipmost non-closed branch head

  $ hg update null
  0 files updated, 0 files merged, 3 files removed, 0 files unresolved
  $ hg branch newbranch
  marked working directory as branch newbranch
  (branches are permanent and global, did you want a bookmark?)
  $ hg update -C
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg summary
  parent: 2:991a3460af53 tip
   c
  branch: default
  commit: (clean)
  update: (current)
  phases: 3 draft