Merge branch 'ma/sha-256-docs'

Further update of docs to adjust to the recent SHA-256 work.

* ma/sha-256-docs:
  shallow.txt: document SHA-256 shallow format
  protocol-capabilities.txt: clarify "allow-x-sha1-in-want" re SHA-256
  index-format.txt: document SHA-256 index format
  http-protocol.txt: document SHA-256 "want"/"have" format

Documentation/technical/http-protocol.txt

@@ -401,8 +401,9 @@ at all in the request stream:
 The stream is terminated by a pkt-line flush (`0000`).
 
 A single "want" or "have" command MUST have one hex formatted
-SHA-1 as its value.  Multiple SHA-1s MUST be sent by sending
+object name as its value.  Multiple object names MUST be sent by sending
-multiple commands.
+multiple commands. Object names MUST be given using the object format
+negotiated through the `object-format` capability (default SHA-1).
 
 The `have` list is created by popping the first 32 commits
 from `c_pending`.  Less can be supplied if `c_pending` empties.

Documentation/technical/index-format.txt

@@ -3,8 +3,11 @@ Git index format
 
 == The Git index file has the following format
 
-  All binary numbers are in network byte order. Version 2 is described
+  All binary numbers are in network byte order.
-  here unless stated otherwise.
+  In a repository using the traditional SHA-1, checksums and object IDs
+  (object names) mentioned below are all computed using SHA-1.  Similarly,
+  in SHA-256 repositories, these values are computed using SHA-256.
+  Version 2 is described here unless stated otherwise.
 
    - A 12-byte header consisting of
 
@@ -32,8 +35,7 @@ Git index format
 
      Extension data
 
-   - 160-bit SHA-1 over the content of the index file before this
+   - Hash checksum over the content of the index file before this checksum.
-     checksum.
 
 == Index entry
 
@@ -80,7 +82,7 @@ Git index format
   32-bit file size
     This is the on-disk size from stat(2), truncated to 32-bit.
 
-  160-bit SHA-1 for the represented object
+  Object name for the represented object
 
   A 16-bit 'flags' field split into (high to low bits)
 
@@ -160,8 +162,8 @@ Git index format
 
   - A newline (ASCII 10); and
 
-  - 160-bit object name for the object that would result from writing
+  - Object name for the object that would result from writing this span
-    this span of index as a tree.
+    of index as a tree.
 
   An entry can be in an invalidated state and is represented by having
   a negative number in the entry_count field. In this case, there is no
@@ -198,7 +200,7 @@ Git index format
     stage 1 to 3 (a missing stage is represented by "0" in this field);
     and
 
-  - At most three 160-bit object names of the entry in stages from 1 to 3
+  - At most three object names of the entry in stages from 1 to 3
     (nothing is written for a missing stage).
 
 === Split index
@@ -211,8 +213,8 @@ Git index format
 
   The extension consists of:
 
-  - 160-bit SHA-1 of the shared index file. The shared index file path
+  - Hash of the shared index file. The shared index file path
-    is $GIT_DIR/sharedindex.<SHA-1>. If all 160 bits are zero, the
+    is $GIT_DIR/sharedindex.<hash>. If all bits are zero, the
     index does not require a shared index file.
 
   - An ewah-encoded delete bitmap, each bit represents an entry in the
@@ -253,10 +255,10 @@ Git index format
 
   - 32-bit dir_flags (see struct dir_struct)
 
-  - 160-bit SHA-1 of $GIT_DIR/info/exclude. Null SHA-1 means the file
+  - Hash of $GIT_DIR/info/exclude. A null hash means the file
     does not exist.
 
-  - 160-bit SHA-1 of core.excludesfile. Null SHA-1 means the file does
+  - Hash of core.excludesfile. A null hash means the file does
     not exist.
 
   - NUL-terminated string of per-dir exclude file name. This usually
@@ -285,13 +287,13 @@ The remaining data of each directory block is grouped by type:
   - An ewah bitmap, the n-th bit records "check-only" bit of
     read_directory_recursive() for the n-th directory.
 
-  - An ewah bitmap, the n-th bit indicates whether SHA-1 and stat data
+  - An ewah bitmap, the n-th bit indicates whether hash and stat data
     is valid for the n-th directory and exists in the next data.
 
   - An array of stat data. The n-th data corresponds with the n-th
     "one" bit in the previous ewah bitmap.
 
-  - An array of SHA-1. The n-th SHA-1 corresponds with the n-th "one" bit
+  - An array of hashes. The n-th hash corresponds with the n-th "one" bit
     in the previous ewah bitmap.
 
   - One NUL.
@@ -330,12 +332,12 @@ The remaining data of each directory block is grouped by type:
 
   - 32-bit offset to the end of the index entries
 
-  - 160-bit SHA-1 over the extension types and their sizes (but not
+  - Hash over the extension types and their sizes (but not
 	their contents).  E.g. if we have "TREE" extension that is N-bytes
 	long, "REUC" extension that is M-bytes long, followed by "EOIE",
 	then the hash would be:
 
-	SHA-1("TREE" + <binary representation of N> +
+	Hash("TREE" + <binary representation of N> +
 		"REUC" + <binary representation of M>)
 
 == Index Entry Offset Table

Documentation/technical/protocol-capabilities.txt

@@ -324,15 +324,19 @@ allow-tip-sha1-in-want
 ----------------------
 
 If the upload-pack server advertises this capability, fetch-pack may
-send "want" lines with SHA-1s that exist at the server but are not
+send "want" lines with object names that exist at the server but are not
-advertised by upload-pack.
+advertised by upload-pack. For historical reasons, the name of this
+capability contains "sha1". Object names are always given using the
+object format negotiated through the 'object-format' capability.
 
 allow-reachable-sha1-in-want
 ----------------------------
 
 If the upload-pack server advertises this capability, fetch-pack may
-send "want" lines with SHA-1s that exist at the server but are not
+send "want" lines with object names that exist at the server but are not
-advertised by upload-pack.
+advertised by upload-pack. For historical reasons, the name of this
+capability contains "sha1". Object names are always given using the
+object format negotiated through the 'object-format' capability.
 
 push-cert=<nonce>
 -----------------

Documentation/technical/shallow.txt

@@ -13,7 +13,7 @@ pretend as if they are root commits (e.g. "git log" traversal
 stops after showing them; "git fsck" does not complain saying
 the commits listed on their "parent" lines do not exist).
 
-Each line contains exactly one SHA-1. When read, a commit_graft
+Each line contains exactly one object name. When read, a commit_graft
 will be constructed, which has nr_parent < 0 to make it easier
 to discern from user provided grafts.