[PATCH v4 00/27] Support multiple checkouts

Phew.. v4 changes are

- address all comments from Junio and Eric (I hope)
- fix "git checkout --to" not working from the linked checkouts
- report unused files (e.g. $GIT_DIR/repos/xx/config) in count-objects -v

Nguyễn Thái Ngọc Duy (27):
  path.c: make get_pathname() return strbuf instead of static buffer
  Convert git_snpath() to strbuf_git_path()
  path.c: rename vsnpath() to do_git_path()
  path.c: group git_path(), git_pathdup() and strbuf_git_path() together
  Make git_path() aware of file relocation in $GIT_DIR
  *.sh: respect $GIT_INDEX_FILE
  reflog: avoid constructing .lock path with git_path
  fast-import: use git_path() for accessing .git dir instead of get_git_dir()
  commit: use SEQ_DIR instead of hardcoding "sequencer"
  Add new environment variable $GIT_COMMON_DIR
  git-sh-setup.sh: use rev-parse --git-path to get $GIT_DIR/objects
  *.sh: avoid hardcoding $GIT_DIR/hooks/...
  git-stash: avoid hardcoding $GIT_DIR/logs/....
  setup.c: convert is_git_directory() to use strbuf
  setup.c: detect $GIT_COMMON_DIR in is_git_directory()
  setup.c: convert check_repository_format_gently to use strbuf
  setup.c: detect $GIT_COMMON_DIR check_repository_format_gently()
  setup.c: support multi-checkout repo setup
  wrapper.c: wrapper to open a file, fprintf then close
  use new wrapper write_file() for simple file writing
  checkout: support checking out into a new working directory
  checkout: clean up half-prepared directories in --to mode
  checkout: detach if the branch is already checked out elsewhere
  prune: strategies for linked checkouts
  gc: style change -- no SP before closing bracket
  gc: support prune --repos
  count-objects: report unused files in $GIT_DIR/repos/...

 Documentation/config.txt               |   8 +
 Documentation/git-checkout.txt         |  34 ++++
 Documentation/git-prune.txt            |   3 +
 Documentation/git-rev-parse.txt        |   8 +
 Documentation/git.txt                  |   9 ++
 Documentation/gitrepository-layout.txt |  75 +++++++--
 builtin/branch.c                       |   4 +-
 builtin/checkout.c                     | 274 +++++++++++++++++++++++++++++++--
 builtin/commit.c                       |   2 +-
 builtin/count-objects.c                |  37 ++++-
 builtin/gc.c                           |  21 ++-
 builtin/init-db.c                      |   7 +-
 builtin/prune.c                        |  74 +++++++++
 builtin/reflog.c                       |   2 +-
 builtin/rev-parse.c                    |  11 ++
 cache.h                                |  10 +-
 compat/mingw.h                         |   1 +
 daemon.c                               |  11 +-
 environment.c                          |  24 ++-
 fast-import.c                          |   5 +-
 git-am.sh                              |  22 +--
 git-compat-util.h                      |   4 +
 git-pull.sh                            |   2 +-
 git-rebase--interactive.sh             |   6 +-
 git-rebase--merge.sh                   |   6 +-
 git-rebase.sh                          |   4 +-
 git-sh-setup.sh                        |   2 +-
 git-stash.sh                           |   6 +-
 path.c                                 | 206 ++++++++++++++++---------
 refs.c                                 |  66 +++++---
 refs.h                                 |   2 +-
 setup.c                                | 124 +++++++++++----
 submodule.c                            |   9 +-
 t/t0060-path-utils.sh                  |  34 ++++
 t/t1501-worktree.sh                    |  76 +++++++++
 t/t1510-repo-setup.sh                  |   1 +
 t/t2025-checkout-to.sh (new +x)        |  57 +++++++
 templates/hooks--applypatch-msg.sample |   4 +-
 templates/hooks--pre-applypatch.sample |   4 +-
 trace.c                                |   1 +
 transport.c                            |   8 +-
 wrapper.c                              |  31 ++++
 42 files changed, 1069 insertions(+), 226 deletions(-)