Merge branch 'nd/multiple-work-trees'

A replacement for contrib/workdir/git-new-workdir that does not
rely on symbolic links and make sharing of objects and refs safer
by making the borrowee and borrowers aware of each other.

* nd/multiple-work-trees: (41 commits)
  prune --worktrees: fix expire vs worktree existence condition
  t1501: fix test with split index
  t2026: fix broken &&-chain
  t2026 needs procondition SANITY
  git-checkout.txt: a note about multiple checkout support for submodules
  checkout: add --ignore-other-wortrees
  checkout: pass whole struct to parse_branchname_arg instead of individual flags
  git-common-dir: make "modules/" per-working-directory directory
  checkout: do not fail if target is an empty directory
  t2025: add a test to make sure grafts is working from a linked checkout
  checkout: don't require a work tree when checking out into a new one
  git_path(): keep "info/sparse-checkout" per work-tree
  count-objects: report unused files in $GIT_DIR/worktrees/...
  gc: support prune --worktrees
  gc: factor out gc.pruneexpire parsing code
  gc: style change -- no SP before closing parenthesis
  checkout: clean up half-prepared directories in --to mode
  checkout: reject if the branch is already checked out elsewhere
  prune: strategies for linked checkouts
  checkout: support checking out into a new working directory
  ...

diff --cc Documentation/config.txt
index 2e5ceaf71974b1e5404de79103648da1829eaf42,2700a1bb834050036d074c9f9b6058aa212344ee..948b8b0e5c8e8639e989d2f14dbd310fe146278b
--- 1/Documentation/config.txt
--- 2/Documentation/config.txt
+++ b/Documentation/config.txt
@@@ -1274,8 -1229,15 +1276,15 @@@ gc.pruneExpire:
        "now" may be used to disable this  grace period and always prune
        unreachable objects immediately.
  
 -gc.pruneworktreesexpire::
++gc.pruneWorktreesExpire::
+       When 'git gc' is run, it will call
+       'prune --worktrees --expire 3.months.ago'.
+       Override the grace period with this config variable. The value
+       "now" may be used to disable the grace period and prune
+       $GIT_DIR/worktrees immediately.
+ 
 -gc.reflogexpire::
 -gc.<pattern>.reflogexpire::
 +gc.reflogExpire::
 +gc.<pattern>.reflogExpire::
        'git reflog expire' removes reflog entries older than
        this time; defaults to 90 days.  With "<pattern>" (e.g.
        "refs/stash") in the middle the setting applies only to

diff --cc Documentation/git-checkout.txt
Simple merge

diff --cc Documentation/git.txt
Simple merge

diff --cc builtin/branch.c
Simple merge

diff --cc builtin/checkout.c
index 4aad49aaa1d984bb6852361118932db0c984491b,8b2bf2093bfe3ce1dbae7d5d7c50886386be6f7b..2f92328db46b4ff81e32b32339ad830c4b76688b
--- 1/builtin/checkout.c
--- 2/builtin/checkout.c
+++ b/builtin/checkout.c
@@@ -20,10 -20,11 +20,11 @@@
  #include "resolve-undo.h"
  #include "submodule.h"
  #include "argv-array.h"
+ #include "sigchain.h"
  
  static const char * const checkout_usage[] = {
 -      N_("git checkout [options] <branch>"),
 -      N_("git checkout [options] [<branch>] -- <file>..."),
 +      N_("git checkout [<options>] <branch>"),
 +      N_("git checkout [<options>] [<branch>] -- <file>..."),
        NULL,
  };
  
@@@ -1134,7 -1340,11 +1365,11 @@@ int cmd_checkout(int argc, const char *
                OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
                         N_("do not limit pathspecs to sparse entries only")),
                OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
 -                              N_("second guess 'git checkout no-such-branch'")),
 +                              N_("second guess 'git checkout <no-such-branch>'")),
+               OPT_FILENAME(0, "to", &opts.new_worktree,
+                          N_("check a branch out in a separate working directory")),
+               OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+                        N_("do not check if another worktree is holding the given ref")),
                OPT_END(),
        };
  

diff --cc builtin/clone.c
Simple merge

diff --cc builtin/commit.c
Simple merge

diff --cc builtin/fetch.c
Simple merge

diff --cc builtin/fsck.c
Simple merge

diff --cc builtin/gc.c
Simple merge

diff --cc builtin/init-db.c
Simple merge

diff --cc builtin/prune.c
Simple merge

diff --cc builtin/receive-pack.c
Simple merge

diff --cc builtin/remote.c
Simple merge

diff --cc builtin/repack.c
Simple merge

diff --cc builtin/rev-parse.c
Simple merge

diff --cc cache.h
index b34447ffcf3a97ee1cec76ce090f274f604b926d,670e8614df9597e5cb445c223cabd4167b112e65..771b775621595e312484295abd9ca768ece6f6ea
--- 1/cache.h
--- 2/cache.h
+++ b/cache.h
@@@ -618,17 -620,8 +621,18 @@@ extern int fsync_object_files
  extern int core_preload_index;
  extern int core_apply_sparse_checkout;
  extern int precomposed_unicode;
 +extern int protect_hfs;
 +extern int protect_ntfs;
+ extern int git_db_env, git_index_env, git_graft_env, git_common_dir_env;
  
 +/*
 + * Include broken refs in all ref iterations, which will
 + * generally choke dangerous operations rather than letting
 + * them silently proceed without taking the broken ref into
 + * account.
 + */
 +extern int ref_paranoia;
 +
  /*
   * The character that begins a commented line in user-editable file
   * that is subject to stripspace.

diff --cc daemon.c
Simple merge

diff --cc environment.c
Simple merge

diff --cc fast-import.c
Simple merge

diff --cc git-am.sh
Simple merge

diff --cc git-rebase--interactive.sh
Simple merge

diff --cc git-sh-setup.sh
Simple merge

diff --cc git.c
Simple merge

diff --cc notes-merge.c
Simple merge

diff --cc path.c
Simple merge

diff --cc refs.c
index 47e4e5380a1e0fc04f8b81837c51c023f35871cf,5ed991bd92856bc8b2c5978923a118b8122a6eb5..0312f052575046f0dd539b19897b61eddc2862e0
--- 1/refs.c
--- 2/refs.c
+++ b/refs.c
@@@ -1643,9 -1618,20 +1649,19 @@@ static const char *resolve_ref_unsafe_1
        }
  }
  
+ const char *resolve_ref_unsafe(const char *refname, int resolve_flags,
+                              unsigned char *sha1, int *flags)
+ {
+       struct strbuf sb_path = STRBUF_INIT;
+       const char *ret = resolve_ref_unsafe_1(refname, resolve_flags,
+                                              sha1, flags, &sb_path);
+       strbuf_release(&sb_path);
+       return ret;
+ }
+ 
  char *resolve_refdup(const char *ref, int resolve_flags, unsigned char *sha1, int *flags)
  {
 -      const char *ret = resolve_ref_unsafe(ref, resolve_flags, sha1, flags);
 -      return ret ? xstrdup(ret) : NULL;
 +      return xstrdup_or_null(resolve_ref_unsafe(ref, resolve_flags, sha1, flags));
  }
  
  /* The argument to filter_refs */
@@@ -2272,9 -2243,9 +2288,9 @@@ int dwim_log(const char *str, int len, 
  static struct ref_lock *lock_ref_sha1_basic(const char *refname,
                                            const unsigned char *old_sha1,
                                            const struct string_list *skip,
 -                                          int flags, int *type_p)
 +                                          unsigned int flags, int *type_p)
  {
-       char *ref_file;
+       const char *ref_file;
        const char *orig_refname = refname;
        struct ref_lock *lock;
        int last_errno = 0;
@@@ -2341,9 -2313,13 +2357,9 @@@
        lock->ref_name = xstrdup(refname);
        lock->orig_ref_name = xstrdup(orig_refname);
        ref_file = git_path("%s", refname);
 -      if (missing)
 -              lock->force_write = 1;
 -      if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
 -              lock->force_write = 1;
  
   retry:
-       switch (safe_create_leading_directories(ref_file)) {
+       switch (safe_create_leading_directories_const(ref_file)) {
        case SCLD_OK:
                break; /* success */
        case SCLD_VANISHED:
@@@ -2956,37 -3010,16 +2976,38 @@@ int log_ref_setup(const char *refname, 
        return 0;
  }
  
- static int log_ref_write(const char *refname, const unsigned char *old_sha1,
-                        const unsigned char *new_sha1, const char *msg)
 +static int log_ref_write_fd(int fd, const unsigned char *old_sha1,
 +                          const unsigned char *new_sha1,
 +                          const char *committer, const char *msg)
 +{
 +      int msglen, written;
 +      unsigned maxlen, len;
 +      char *logrec;
 +
 +      msglen = msg ? strlen(msg) : 0;
 +      maxlen = strlen(committer) + msglen + 100;
 +      logrec = xmalloc(maxlen);
 +      len = sprintf(logrec, "%s %s %s\n",
 +                    sha1_to_hex(old_sha1),
 +                    sha1_to_hex(new_sha1),
 +                    committer);
 +      if (msglen)
 +              len += copy_msg(logrec + len - 1, msg) - 1;
 +
 +      written = len <= maxlen ? write_in_full(fd, logrec, len) : -1;
 +      free(logrec);
 +      if (written != len)
 +              return -1;
 +
 +      return 0;
 +}
 +
+ static int log_ref_write_1(const char *refname, const unsigned char *old_sha1,
+                          const unsigned char *new_sha1, const char *msg,
+                          struct strbuf *sb_log_file)
  {
 -      int logfd, result, written, oflags = O_APPEND | O_WRONLY;
 -      unsigned maxlen, len;
 -      int msglen;
 -      const char *log_file;
 -      char *logrec;
 -      const char *committer;
 +      int logfd, result, oflags = O_APPEND | O_WRONLY;
-       char log_file[PATH_MAX];
++      char *log_file;
  
        if (log_all_ref_updates < 0)
                log_all_ref_updates = !is_bare_repository();

diff --cc refs.h
Simple merge

diff --cc run-command.c
Simple merge

diff --cc run-command.h
Simple merge

diff --cc sha1_file.c
Simple merge

diff --cc submodule.c
Simple merge

diff --cc trace.c
Simple merge

diff --cc transport.c
Simple merge

diff --cc wrapper.c
Simple merge