tests/test-impexp-branch.t

dispatch: make loading extra information from extension extensible

This patch makes loading extra information from extension module at
dispatching extensible. Factoring 'loadcmdtable()' into commands.py is
a part of generalization of loading extra information.

This extensibility assumes registration of new function like below,
for example:

  - revset predicate
  - fileset predicate
  - template keyword
  - template filter
  - template function
  - internal merge tool
  - web command

This patch requires not loader function itself but container module
and the name of it, because listing loader function directly up
implies actual loading module of it, even if it isn't used at runtime
(for example, extensions don't always define revset predicate)

  $ echo '[extensions]' >> $HGRCPATH
  $ echo 'strip =' >> $HGRCPATH

  $ cat >findbranch.py <<EOF
  > import re, sys
  > 
  > head_re = re.compile('^#(?:(?:\\s+([A-Za-z][A-Za-z0-9_]*)(?:\\s.*)?)|(?:\\s*))$')
  > 
  > for line in sys.stdin:
  >     hmatch = head_re.match(line)
  >     if not hmatch:
  >         sys.exit(1)
  >     if hmatch.group(1) == 'Branch':
  >         sys.exit(0)
  > sys.exit(1)
  > EOF

  $ hg init a
  $ cd a
  $ echo "Rev 1" >rev
  $ hg add rev
  $ hg commit -m "No branch."
  $ hg branch abranch
  marked working directory as branch abranch
  (branches are permanent and global, did you want a bookmark?)
  $ echo "Rev  2" >rev
  $ hg commit -m "With branch."

  $ hg export 0 > ../r0.patch
  $ hg export 1 > ../r1.patch
  $ cd ..

  $ if python findbranch.py < r0.patch; then
  >     echo "Export of default branch revision has Branch header" 1>&2
  >     exit 1
  > fi

  $ if python findbranch.py < r1.patch; then
  >     :  # Do nothing
  > else
  >     echo "Export of branch revision is missing Branch header" 1>&2
  >     exit 1
  > fi

Make sure import still works with branch information in patches.

  $ hg init b
  $ cd b
  $ hg import ../r0.patch
  applying ../r0.patch
  $ hg import ../r1.patch
  applying ../r1.patch
  $ cd ..

  $ hg init c
  $ cd c
  $ hg import --exact --no-commit ../r0.patch
  applying ../r0.patch
  warning: can't check exact import with --no-commit
  $ hg st
  A rev
  $ hg revert -a
  forgetting rev
  $ rm rev
  $ hg import --exact ../r0.patch
  applying ../r0.patch
  $ hg import --exact ../r1.patch
  applying ../r1.patch

Test --exact and patch header separators (issue3356)

  $ hg strip --no-backup .
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  >>> import re
  >>> p = file('../r1.patch', 'rb').read()
  >>> p = re.sub(r'Parent\s+', 'Parent ', p)
  >>> file('../r1-ws.patch', 'wb').write(p)
  $ hg import --exact ../r1-ws.patch
  applying ../r1-ws.patch

  $ cd ..