Documentation: add documentation for "git replace"

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-replace.txt

@@ -0,0 +1,71 @@
+git-replace(1)
+==============
+
+NAME
+----
+git-replace - Create, list, delete refs to replace objects
+
+SYNOPSIS
+--------
+[verse]
+'git replace' [-f] <object> <replacement>
+'git replace' -d <object>...
+'git replace' -l [<pattern>]
+
+DESCRIPTION
+-----------
+Adds a 'replace' reference in `.git/refs/replace/`
+
+The name of the 'replace' reference is the SHA1 of the object that is
+replaced. The content of the replace reference is the SHA1 of the
+replacement object.
+
+Unless `-f` is given, the replace reference must not yet exist in
+`.git/refs/replace/` directory.
+
+OPTIONS
+-------
+-f::
+	If an existing replace ref for the same object exists, it will
+	be overwritten (instead of failing).
+
+-d::
+	Delete existing replace refs for the given objects.
+
+-l <pattern>::
+	List replace refs for objects that match the given pattern (or
+	all if no pattern is given).
+	Typing "git replace" without arguments, also lists all replace
+	refs.
+
+BUGS
+----
+Comparing blobs or trees that have been replaced with those that
+replace them will not work properly. And using 'git reset --hard' to
+go back to a replaced commit will move the branch to the replacement
+commit instead of the replaced commit.
+
+There may be other problems when using 'git rev-list' related to
+pending objects. And of course things may break if an object of one
+type is replaced by an object of another type (for example a blob
+replaced by a commit).
+
+SEE ALSO
+--------
+linkgit:git-tag[1]
+linkgit:git-branch[1]
+
+Author
+------
+Written by Christian Couder <chriscool@tuxfamily.org> and Junio C
+Hamano <gitster@pobox.com>, based on 'git tag' by Kristian Hogsberg
+<krh@redhat.com> and Carlos Rica <jasampler@gmail.com>.
+
+Documentation
+--------------
+Documentation by Christian Couder <chriscool@tuxfamily.org> and the
+git-list <git@vger.kernel.org>, based on 'git tag' documentation.
+
+GIT
+---
+Part of the linkgit:git[1] suite