tests/test-wireproto-command-branchmap.t

discovery-helper: use reflink copy if available

A reflink copy will copy the files "as usual" but keep using the same data block
underneath. This is only supported by "copy on write" file system like btrfs or
zfs.

This will achieve similar performance that the existing hardlink clone that
Mercurial performs with the same initial space saving. However, it will behave
better on revlogs start being touch by strip. Instead of duplicating all data in
the touched revlogs, only the block actually affected by the strip will be
duplicated. This save a lot of space when building many variants of large
repositories.

The --reflink=always flag make sure the `cp` call fails if reflink copies are
not supported. Falling back to local clone.

  $ . $TESTDIR/wireprotohelpers.sh

  $ hg init server
  $ enablehttpv2 server
  $ cd server
  $ hg debugdrawdag << EOF
  > C D
  > |/
  > B
  > |
  > A
  > EOF

  $ hg up B
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch branch1
  marked working directory as branch branch1
  (branches are permanent and global, did you want a bookmark?)
  $ echo b1 > foo
  $ hg -q commit -A -m 'branch 1'
  $ hg up B
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg branch branch2
  marked working directory as branch branch2
  $ echo b2 > foo
  $ hg -q commit -A -m 'branch 2'

  $ hg log -T '{rev}:{node} {branch} {desc}\n'
  5:224161c7589aa48fa83a48feff5e95b56ae327fc branch2 branch 2
  4:b5faacdfd2633768cb3152336cc0953381266688 branch1 branch 1
  3:be0ef73c17ade3fc89dc41701eb9fc3a91b58282 default D
  2:26805aba1e600a82e93661149f2313866a221a7b default C
  1:112478962961147124edd43549aedd1a335e44bf default B
  0:426bada5c67598ca65036d57d9e4b64b0c1ce7a0 default A

  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
  $ cat hg.pid > $DAEMON_PIDS

No arguments returns something reasonable

  $ sendhttpv2peer << EOF
  > command branchmap
  > EOF
  creating http peer for wire protocol version 2
  sending branchmap command
  response: {
    b'branch1': [
      b'\xb5\xfa\xac\xdf\xd2c7h\xcb1R3l\xc0\x953\x81&f\x88'
    ],
    b'branch2': [
      b'"Aa\xc7X\x9a\xa4\x8f\xa8:H\xfe\xff^\x95\xb5j\xe3\'\xfc'
    ],
    b'default': [
      b'&\x80Z\xba\x1e`\n\x82\xe96a\x14\x9f#\x13\x86j"\x1a{',
      b'\xbe\x0e\xf7<\x17\xad\xe3\xfc\x89\xdcAp\x1e\xb9\xfc:\x91\xb5\x82\x82'
    ]
  }

  $ cat error.log