Merge branch 'lj/refs'

* lj/refs: (63 commits)
  Fix show-ref usagestring
  t3200: git-branch testsuite update
  sha1_name.c: avoid compilation warnings.
  Make git-branch a builtin
  ref-log: fix D/F conflict coming from deleted refs.
  git-revert with conflicts to behave as git-merge with conflicts
  core.logallrefupdates thinko-fix
  git-pack-refs --all
  core.logallrefupdates create new log file only for branch heads.
  Remove bashism from t3210-pack-refs.sh
  ref-log: allow ref@{count} syntax.
  pack-refs: call fflush before fsync.
  pack-refs: use lockfile as everybody else does.
  git-fetch: do not look into $GIT_DIR/refs to see if a tag exists.
  lock_ref_sha1_basic does not remove empty directories on BSD
  Do not create tag leading directories since git update-ref does it.
  Check that a tag exists using show-ref instead of looking for the ref file.
  Use git-update-ref to delete a tag instead of rm()ing the ref file.
  Fix refs.c;:repack_without_ref() clean-up path
  Clean up "git-branch.sh" and add remove recursive dir test cases.
  ...

3 files changed, 174 insertions, 8 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 026d4cf9ad..d9e73da2a7 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -71,12 +71,16 @@ core.preferSymlinkRefs::
 	expect HEAD to be a symbolic link.
 
 core.logAllRefUpdates::
-	If true, `git-update-ref` will append a line to
-	"$GIT_DIR/logs/<ref>" listing the new SHA1 and the date/time
-	of the update.	If the file does not exist it will be
-	created automatically.	This information can be used to
-	determine what commit was the tip of a branch "2 days ago".
-	This value is false by default (no logging).
+	Updates to a ref <ref> is logged to the file
+	"$GIT_DIR/logs/<ref>", by appending the new and old
+	SHA1, the date/time and the reason of the update, but
+	only when the file exists.  If this configuration
+	variable is set to true, missing "$GIT_DIR/logs/<ref>"
+	file is automatically created for branch heads.
+
+	This information can be used to determine what commit
+	was the tip of a branch "2 days ago".  This value is
+	false by default (no automated creation of log files).
 
 core.repositoryFormatVersion::
 	Internal variable identifying the repository format and layout
diff --git a/Documentation/git-show-ref.txt b/Documentation/git-show-ref.txt
new file mode 100644
index 0000000000..5973a82517
--- /dev/null
+++ b/Documentation/git-show-ref.txt
@@ -0,0 +1,156 @@
+git-show-ref(1)
+===============
+
+NAME
+----
+git-show-ref - List references in a local repository
+
+SYNOPSIS
+--------
+[verse]
+'git-show-ref' [-q|--quiet] [--verify] [-h|--head] [-d|--dereference]
+	     [-s|--hash] [--abbrev] [--tags] [--heads] [--] <pattern>...
+
+DESCRIPTION
+-----------
+
+Displays references available in a local repository along with the associated
+commit IDs. Results can be filtered using a pattern and tags can be
+dereferenced into object IDs. Additionally, it can be used to test whether a
+particular ref exists.
+
+Use of this utility is encouraged in favor of directly accessing files under
+in the `.git` directory.
+
+OPTIONS
+-------
+
+-h, --head::
+
+	Show the HEAD reference.
+
+--tags, --heads::
+
+	Limit to only "refs/heads" and "refs/tags", respectively.  These
+	options are not mutually exclusive; when given both, references stored
+	in "refs/heads" and "refs/tags" are displayed.
+
+-d, --dereference::
+
+	Dereference tags into object IDs as well. They will be shown with "^{}"
+	appended.
+
+-s, --hash::
+
+	Only show the SHA1 hash, not the reference name. When also using
+	--dereference the dereferenced tag will still be shown after the SHA1.
+
+--verify::
+
+	Enable stricter reference checking by requiring an exact ref path.
+	Aside from returning an error code of 1, it will also print an error
+	message if '--quiet' was not specified.
+
+--abbrev, --abbrev=len::
+
+	Abbreviate the object name.  When using `--hash`, you do
+	not have to say `--hash --abbrev`; `--hash=len` would do.
+
+-q, --quiet::
+
+	Do not print any results to stdout. When combined with '--verify' this
+	can be used to silently check if a reference exists.
+
+<pattern>::
+
+	Show references matching one or more patterns.
+
+OUTPUT
+------
+
+The output is in the format: '<SHA-1 ID>' '<space>' '<reference name>'.
+
+-----------------------------------------------------------------------------
+$ git show-ref --head --dereference
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 HEAD
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/master
+832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/origin
+3521017556c5de4159da4615a39fa4d5d2c279b5 refs/tags/v0.99.9c
+6ddc0964034342519a87fe013781abf31c6db6ad refs/tags/v0.99.9c^{}
+055e4ae3ae6eb344cbabf2a5256a49ea66040131 refs/tags/v1.0rc4
+423325a2d24638ddcc82ce47be5e40be550f4507 refs/tags/v1.0rc4^{}
+...
+-----------------------------------------------------------------------------
+
+When using --hash (and not --dereference) the output format is: '<SHA-1 ID>'
+
+-----------------------------------------------------------------------------
+$ git show-ref --heads --hash
+2e3ba0114a1f52b47df29743d6915d056be13278
+185008ae97960c8d551adcd9e23565194651b5d1
+03adf42c988195b50e1a1935ba5fcbc39b2b029b
+...
+-----------------------------------------------------------------------------
+
+EXAMPLE
+-------
+
+To show all references called "master", whether tags or heads or anything
+else, and regardless of how deep in the reference naming hierarchy they are,
+use:
+
+-----------------------------------------------------------------------------
+	git show-ref master
+-----------------------------------------------------------------------------
+
+This will show "refs/heads/master" but also "refs/remote/other-repo/master",
+if such references exists.
+
+When using the '--verify' flag, the command requires an exact path:
+
+-----------------------------------------------------------------------------
+	git show-ref --verify refs/heads/master
+-----------------------------------------------------------------------------
+
+will only match the exact branch called "master".
+
+If nothing matches, gitlink:git-show-ref[1] will return an error code of 1,
+and in the case of verification, it will show an error message.
+
+For scripting, you can ask it to be quiet with the "--quiet" flag, which
+allows you to do things like
+
+-----------------------------------------------------------------------------
+	git-show-ref --quiet --verify -- "refs/heads/$headname" ||
+		echo "$headname is not a valid branch"
+-----------------------------------------------------------------------------
+
+to check whether a particular branch exists or not (notice how we don't
+actually want to show any results, and we want to use the full refname for it
+in order to not trigger the problem with ambiguous partial matches).
+
+To show only tags, or only proper branch heads, use "--tags" and/or "--heads"
+respectively (using both means that it shows tags and heads, but not other
+random references under the refs/ subdirectory).
+
+To do automatic tag object dereferencing, use the "-d" or "--dereference"
+flag, so you can do
+
+-----------------------------------------------------------------------------
+	git show-ref --tags --dereference
+-----------------------------------------------------------------------------
+
+to get a listing of all tags together with what they dereference.
+
+SEE ALSO
+--------
+gitlink:git-ls-remote[1], gitlink:git-peek-remote[1]
+
+AUTHORS
+-------
+Written by Linus Torvalds <torvalds@osdl.org>.
+Man page by Jonas Fonseca <fonseca@diku.dk>.
+
+GIT
+---
+Part of the gitlink:git[7] suite
diff --git a/Documentation/git-update-ref.txt b/Documentation/git-update-ref.txt
index e062030e91..71bcb7954f 100644
--- a/Documentation/git-update-ref.txt
+++ b/Documentation/git-update-ref.txt
@@ -7,7 +7,7 @@ git-update-ref - update the object name stored in a ref safely
 
 SYNOPSIS
 --------
-'git-update-ref' [-m <reason>] <ref> <newvalue> [<oldvalue>]
+'git-update-ref' [-m <reason>] (-d <ref> <oldvalue> | <ref> <newvalue> [<oldvalue>])
 
 DESCRIPTION
 -----------
@@ -20,7 +20,9 @@ possibly dereferencing the symbolic refs, after verifying that
 the current value of the <ref> matches <oldvalue>.
 E.g. `git-update-ref refs/heads/master <newvalue> <oldvalue>`
 updates the master branch head to <newvalue> only if its current
-value is <oldvalue>.
+value is <oldvalue>.  You can specify 40 "0" or an empty string
+as <oldvalue> to make sure that the ref you are creating does
+not exist.
 
 It also allows a "ref" file to be a symbolic pointer to another
 ref file by starting with the four-byte header sequence of
@@ -49,6 +51,10 @@ for reading but not for writing (so we'll never write through a
 ref symlink to some other tree, if you have copied a whole
 archive by creating a symlink tree).
 
+With `-d` flag, it deletes the named <ref> after verifying it
+still contains <oldvalue>.
+
+
 Logging Updates
 ---------------
 If config parameter "core.logAllRefUpdates" is true or the file