6 files changed, 153 insertions, 11 deletions
diff --git a/Documentation/technical/api-directory-listing.txt b/Documentation/technical/api-directory-listing.txt
index 4f44ca24f6..5abb8e8b1f 100644
--- a/Documentation/technical/api-directory-listing.txt
+++ b/Documentation/technical/api-directory-listing.txt
@@ -54,7 +54,7 @@ The notable options are:
 	this case, the contents are returned as individual entries.
 +
 If this is set, files and directories that explicitly match an ignore
-pattern are reported. Implicity ignored directories (directories that
+pattern are reported. Implicitly ignored directories (directories that
 do not match an ignore pattern, but whose contents are all ignored)
 are not reported, instead all of the contents are reported.
 
diff --git a/Documentation/technical/api-gitattributes.txt b/Documentation/technical/api-gitattributes.txt
index e7cbb7c13a..45f0df600f 100644
--- a/Documentation/technical/api-gitattributes.txt
+++ b/Documentation/technical/api-gitattributes.txt
@@ -146,7 +146,7 @@ To get the values of all attributes associated with a file:
 
 * Iterate over the `attr_check.items[]` array to examine
   the attribute names and values.  The name of the attribute
-  described by a  `attr_check.items[]` object can be retrieved via
+  described by an `attr_check.items[]` object can be retrieved via
   `git_attr_name(check->items[i].attr)`.  (Please note that no items
   will be returned for unset attributes, so `ATTR_UNSET()` will return
   false for all returned `attr_check.items[]` objects.)
diff --git a/Documentation/technical/commit-graph-format.txt b/Documentation/technical/commit-graph-format.txt
index ad6af8105c..cc0474ba3e 100644
--- a/Documentation/technical/commit-graph-format.txt
+++ b/Documentation/technical/commit-graph-format.txt
@@ -18,9 +18,9 @@ metadata, including:
   the graph file.
 
 These positional references are stored as unsigned 32-bit integers
-corresponding to the array position withing the list of commit OIDs. We
-use the most-significant bit for special purposes, so we can store at most
-(1 << 31) - 1 (around 2 billion) commits.
+corresponding to the array position within the list of commit OIDs. Due
+to some special constants we use to track parents, we can store at most
+(1 << 30) + (1 << 29) + (1 << 28) - 1 (around 1.8 billion) commits.
 
 == Commit graph files have the following format:
 
@@ -70,10 +70,10 @@ CHUNK DATA:
   OID Lookup (ID: {'O', 'I', 'D', 'L'}) (N * H bytes)
       The OIDs for all commits in the graph, sorted in ascending order.
 
-  Commit Data (ID: {'C', 'G', 'E', 'T' }) (N * (H + 16) bytes)
+  Commit Data (ID: {'C', 'D', 'A', 'T' }) (N * (H + 16) bytes)
     * The first H bytes are for the OID of the root tree.
     * The next 8 bytes are for the positions of the first two parents
-      of the ith commit. Stores value 0xffffffff if no parent in that
+      of the ith commit. Stores value 0x7000000 if no parent in that
       position. If there are more than two parents, the second value
       has its most-significant bit on and the other bits store an array
       position into the Large Edge List chunk.
diff --git a/Documentation/technical/directory-rename-detection.txt b/Documentation/technical/directory-rename-detection.txt
new file mode 100644
index 0000000000..1c0086e287
--- /dev/null
+++ b/Documentation/technical/directory-rename-detection.txt
@@ -0,0 +1,115 @@
+Directory rename detection
+==========================
+
+Rename detection logic in diffcore-rename that checks for renames of
+individual files is aggregated and analyzed in merge-recursive for cases
+where combinations of renames indicate that a full directory has been
+renamed.
+
+Scope of abilities
+------------------
+
+It is perhaps easiest to start with an example:
+
+  * When all of x/a, x/b and x/c have moved to z/a, z/b and z/c, it is
+    likely that x/d added in the meantime would also want to move to z/d by
+    taking the hint that the entire directory 'x' moved to 'z'.
+
+More interesting possibilities exist, though, such as:
+
+  * one side of history renames x -> z, and the other renames some file to
+    x/e, causing the need for the merge to do a transitive rename.
+
+  * one side of history renames x -> z, but also renames all files within
+    x.  For example, x/a -> z/alpha, x/b -> z/bravo, etc.
+
+  * both 'x' and 'y' being merged into a single directory 'z', with a
+    directory rename being detected for both x->z and y->z.
+
+  * not all files in a directory being renamed to the same location;
+    i.e. perhaps most the files in 'x' are now found under 'z', but a few
+    are found under 'w'.
+
+  * a directory being renamed, which also contained a subdirectory that was
+    renamed to some entirely different location.  (And perhaps the inner
+    directory itself contained inner directories that were renamed to yet
+    other locations).
+
+  * combinations of the above; see t/t6043-merge-rename-directories.sh for
+    various interesting cases.
+
+Limitations -- applicability of directory renames
+-------------------------------------------------
+
+In order to prevent edge and corner cases resulting in either conflicts
+that cannot be represented in the index or which might be too complex for
+users to try to understand and resolve, a couple basic rules limit when
+directory rename detection applies:
+
+  1) If a given directory still exists on both sides of a merge, we do
+     not consider it to have been renamed.
+
+  2) If a subset of to-be-renamed files have a file or directory in the
+     way (or would be in the way of each other), "turn off" the directory
+     rename for those specific sub-paths and report the conflict to the
+     user.
+
+  3) If the other side of history did a directory rename to a path that
+     your side of history renamed away, then ignore that particular
+     rename from the other side of history for any implicit directory
+     renames (but warn the user).
+
+Limitations -- detailed rules and testcases
+-------------------------------------------
+
+t/t6043-merge-rename-directories.sh contains extensive tests and commentary
+which generate and explore the rules listed above.  It also lists a few
+additional rules:
+
+  a) If renames split a directory into two or more others, the directory
+     with the most renames, "wins".
+
+  b) Avoid directory-rename-detection for a path, if that path is the
+     source of a rename on either side of a merge.
+
+  c) Only apply implicit directory renames to directories if the other side
+     of history is the one doing the renaming.
+
+Limitations -- support in different commands
+--------------------------------------------
+
+Directory rename detection is supported by 'merge' and 'cherry-pick'.
+Other git commands which users might be surprised to see limited or no
+directory rename detection support in:
+
+  * diff
+
+    Folks have requested in the past that `git diff` detect directory
+    renames and somehow simplify its output.  It is not clear whether this
+    would be desirable or how the output should be simplified, so this was
+    simply not implemented.  Further, to implement this, directory rename
+    detection logic would need to move from merge-recursive to
+    diffcore-rename.
+
+  * am
+
+    git-am tries to avoid a full three way merge, instead calling
+    git-apply.  That prevents us from detecting renames at all, which may
+    defeat the directory rename detection.  There is a fallback, though; if
+    the initial git-apply fails and the user has specified the -3 option,
+    git-am will fall back to a three way merge.  However, git-am lacks the
+    necessary information to do a "real" three way merge.  Instead, it has
+    to use build_fake_ancestor() to get a merge base that is missing files
+    whose rename may have been important to detect for directory rename
+    detection to function.
+
+  * rebase
+
+    Since am-based rebases work by first generating a bunch of patches
+    (which no longer record what the original commits were and thus don't
+    have the necessary info from which we can find a real merge-base), and
+    then calling git-am, this implies that am-based rebases will not always
+    successfully detect directory renames either (see the 'am' section
+    above).  merged-based rebases (rebase -m) and cherry-pick-based rebases
+    (rebase -i) are not affected by this shortcoming, and fully support
+    directory rename detection.
diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index 7fee6b780a..508a344cf1 100644
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -284,7 +284,9 @@ information is sent back to the client in the next step.
 The client can optionally request that pack-objects omit various
 objects from the packfile using one of several filtering techniques.
 These are intended for use with partial clone and partial fetch
-operations.  See `rev-list` for possible "filter-spec" values.
+operations. An object that does not meet a filter-spec value is
+omitted unless explicitly requested in a 'want' line. See `rev-list`
+for possible filter-spec values.
 
 Once all the 'want's and 'shallow's (and optional 'deepen') are
 transferred, clients MUST send a flush-pkt, to tell the server side
diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index 49bda76d23..09e4e0273f 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -64,9 +64,8 @@ When using the http:// or https:// transport a client makes a "smart"
 info/refs request as described in `http-protocol.txt` and requests that
 v2 be used by supplying "version=2" in the `Git-Protocol` header.
 
-   C: Git-Protocol: version=2
-   C:
    C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0
+   C: Git-Protocol: version=2
 
 A v2 server would reply:
 
@@ -299,12 +298,21 @@ included in the client's request:
 	for use with partial clone and partial fetch operations. See
 	`rev-list` for possible "filter-spec" values.
 
+If the 'ref-in-want' feature is advertised, the following argument can
+be included in the client's request as well as the potential addition of
+the 'wanted-refs' section in the server's response as explained below.
+
+    want-ref <ref>
+	Indicates to the server that the client wants to retrieve a
+	particular ref, where <ref> is the full name of a ref on the
+	server.
+
 The response of `fetch` is broken into a number of sections separated by
 delimiter packets (0001), with each section beginning with its section
 header.
 
     output = *section
-    section = (acknowledgments | shallow-info | packfile)
+    section = (acknowledgments | shallow-info | wanted-refs | packfile)
 	      (flush-pkt | delim-pkt)
 
     acknowledgments = PKT-LINE("acknowledgments" LF)
@@ -319,6 +327,10 @@ header.
     shallow = "shallow" SP obj-id
     unshallow = "unshallow" SP obj-id
 
+    wanted-refs = PKT-LINE("wanted-refs" LF)
+		  *PKT-LINE(wanted-ref LF)
+    wanted-ref = obj-id SP refname
+
     packfile = PKT-LINE("packfile" LF)
 	       *PKT-LINE(%x01-03 *%x00-ff)
 
@@ -379,6 +391,19 @@ header.
 	* This section is only included if a packfile section is also
 	  included in the response.
 
+    wanted-refs section
+	* This section is only included if the client has requested a
+	  ref using a 'want-ref' line and if a packfile section is also
+	  included in the response.
+
+	* Always begins with the section header "wanted-refs".
+
+	* The server will send a ref listing ("<oid> <refname>") for
+	  each reference requested using 'want-ref' lines.
+
+	* The server MUST NOT send any refs which were not requested
+	  using 'want-ref' lines.
+
     packfile section
 	* This section is only included if the client has sent 'want'
 	  lines in its request and either requested that no more