SHA256E is new default backend

The default backend used when adding files to the annex is changed from
SHA256 to SHA256E, to simplify interoperability with OSX, media players,
and various programs that needlessly look at symlink targets.

To get old behavior, add a .gitattributes containing: * annex.backend=SHA256

Backend/SHA.hs

@@ -1,4 +1,4 @@
-{- git-annex SHA backend
+{- git-annex SHA backends
  -
  - Copyright 2011,2012 Joey Hess <joey@kitenet.net>
  -
@@ -19,13 +19,14 @@ import qualified Data.ByteString.Lazy as L
 
 type SHASize = Int
 
--- order is slightly significant; want SHA256 first, and more general
+{- Order is slightly significant; want SHA256 first, and more general
--- sizes earlier
+ - sizes earlier. -}
 sizes :: [Int]
 sizes = [256, 1, 512, 224, 384]
 
+{- The SHA256E backend is the default. -}
 backends :: [Backend]
-backends = catMaybes $ map genBackend sizes ++ map genBackendE sizes
+backends = catMaybes $ map genBackendE sizes ++ map genBackend sizes
 
 genBackend :: SHASize -> Maybe Backend
 genBackend size = Just $ Backend

debian/changelog

@@ -4,6 +4,10 @@ git-annex (3.20120826) UNRELEASED; urgency=low
     as well as automatically syncing file contents between repositories.
   * webapp: New command (and FreeDesktop menu item) that allows managing
     and configuring the assistant in a web browser.
+  * The default backend used when adding files to the annex is changed
+    from SHA256 to SHA256E, to simplify interoperability with OSX, media
+    players, and various programs that needlessly look at symlink targets.
+    To get old behavior, add a .gitattributes containing: * annex.backend=SHA256
   * init: If no description is provided for a new repository, one will
     automatically be generated, like "joey@gnu:~/foo"
   * test: Set a lot of git environment variables so testing works in strange

doc/backends.mdwn

@@ -5,21 +5,21 @@ to retrieve the file's content (its value).
 Multiple pluggable key-value backends are supported, and a single repository
 can use different ones for different files.
 
-* `SHA256` -- The default backend for new files. This allows
+* `SHA256E` -- The default backend for new files. This allows
   verifying that the file content is right, and can avoid duplicates of
   files with the same content. Its need to generate checksums
   can make it slower for large files. 
+* `SHA256` -- Does not include the file extension in the key, which can
+  lead to better deduplication.
 * `WORM` ("Write Once, Read Many") This assumes that any file with
   the same basename, size, and modification time has the same content.
   This is the the least expensive backend, recommended for really large
   files or slow systems.
-* `SHA512` -- Best currently available hash, for the very paranoid.
+* `SHA512`, `SHA512E` -- Best currently available hash, for the very paranoid.
-* `SHA1` -- Smaller hash than `SHA256` for those who want a checksum
+* `SHA1`, `SHA1E` -- Smaller hash than `SHA256` for those who want a checksum
    but are not concerned about security.
-* `SHA384`, `SHA224` -- Hashes for people who like unusual sizes.
+* `SHA384`, `SHA384E`, `SHA224`, `SHA224E` -- Hashes for people who like
-* `SHA256E`, `SHA1E`, etc -- Variants that preserve filename extension as
+  unusual sizes.
-  part of the key. Useful for archival tasks where the filename extension
-  contains metadata that should be preserved.
 
 The `annex.backends` git-config setting can be used to list the backends
 git-annex should use. The first one listed will be used by default when
@@ -29,11 +29,11 @@ For finer control of what backend is used when adding different types of
 files, the `.gitattributes` file can be used. The `annex.backend`
 attribute can be set to the name of the backend to use for matching files.
 
-For example, to use the SHA256 backend for sound files, which tend to be
+For example, to use the SHA256E backend for sound files, which tend to be
 smallish and might be modified or copied over time,
 while using the WORM backend for everything else, you could set
 in `.gitattributes`:
 
 	* annex.backend=WORM
-	*.mp3 annex.backend=SHA256
+	*.mp3 annex.backend=SHA256E
-	*.ogg annex.backend=SHA256
+	*.ogg annex.backend=SHA256E

doc/git-annex.mdwn

@@ -801,10 +801,10 @@ The key-value backend used when adding a new file to the annex can be
 configured on a per-file-type basis via `.gitattributes` files. In the file,
 the `annex.backend` attribute can be set to the name of the backend to
 use. For example, this here's how to use the WORM backend by default,
-but the SHA1 backend for ogg files:
+but the SHA256E backend for ogg files:
 
 	* annex.backend=WORM
-	*.ogg annex.backend=SHA1
+	*.ogg annex.backend=SHA256E
 
 The numcopies setting can also be configured on a per-file-type basis via
 the `annex.numcopies` attribute in `.gitattributes` files.