git annex add -u now supported, analagous to git add -u

Unlike git add -u, git annex add -u does not update the index for files
removed from the working tree. But then, "git add ." stages removals,
and "git annex add ." does not, so that's an existing divergence.

Seems that --update --batch would need to run git ls-files once per line of
batch input, which would surely be too slow, so just throw an error for
that.

This commit was supported by the NSF-funded DataLad project.

5 files changed, 28 insertions, 3 deletions

diff --git a/CHANGELOG b/CHANGELOG
index c53b01c52..d988a969e 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -19,6 +19,7 @@ git-annex (6.20170322) UNRELEASED; urgency=medium
     ignored, a reversion introduced in 6.20160527.
   * gcrypt: Support re-enabling to change eg, encryption parameters.
     This was never supported before.
+  * git annex add -u now supported, analagous to git add -u
 
  -- Joey Hess <id@joeyh.name>  Wed, 29 Mar 2017 12:41:46 -0400
 
diff --git a/Command/Add.hs b/Command/Add.hs
index f9cfbb9a1..beea48e0b 100644
--- a/Command/Add.hs
+++ b/Command/Add.hs
@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2010, 2013 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2017 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -30,6 +30,7 @@ data AddOptions = AddOptions
 	{ addThese :: CmdParams
 	, includeDotFiles :: Bool
 	, batchOption :: BatchMode
+	, updateOnly :: Bool
 	}
 
 optParser :: CmdParamsDesc -> Parser AddOptions
@@ -40,6 +41,11 @@ optParser desc = AddOptions
 		<> help "don't skip dotfiles"
 		)
 	<*> parseBatchOption
+	<*> switch
+		( long "update"
+		<> short 'u'
+		<> help "only update tracked files"
+		)
 
 seek :: AddOptions -> CommandSeek
 seek o = allowConcurrentOutput $ do
@@ -52,10 +58,14 @@ seek o = allowConcurrentOutput $ do
 			)
 		)
 	case batchOption o of
-		Batch -> batchFiles gofile
+		Batch
+			| updateOnly o ->
+				giveup "--update --batch is not supported"
+			| otherwise -> batchFiles gofile
 		NoBatch -> do
 			let go a = a gofile (addThese o)
-			go (withFilesNotInGit (not $ includeDotFiles o))
+			unless (updateOnly o) $
+				go (withFilesNotInGit (not $ includeDotFiles o))
 			go withFilesMaybeModified
 			unlessM (versionSupportsUnlockedPointers <||> isDirect) $
 				go withFilesOldUnlocked
diff --git a/doc/git-annex-add.mdwn b/doc/git-annex-add.mdwn
index 15bb8a6a0..2ebbbac06 100644
--- a/doc/git-annex-add.mdwn
+++ b/doc/git-annex-add.mdwn
@@ -56,6 +56,11 @@ annexed content, and other symlinks.
   Adds multiple files in parallel. This may be faster.
   For example: `-J4`  
 
+* `--update` `-u`
+
+  Like `git add --update`, this does not add new files, but any updates
+  to tracked files will be added to the index.
+
 * `--json`
 
   Enable JSON output. This is intended to be parsed by programs that use
diff --git a/doc/todo/annex_add___40__-u__124__--update__41___mode.mdwn b/doc/todo/annex_add___40__-u__124__--update__41___mode.mdwn
index 833117652..ab0eac108 100644
--- a/doc/todo/annex_add___40__-u__124__--update__41___mode.mdwn
+++ b/doc/todo/annex_add___40__-u__124__--update__41___mode.mdwn
@@ -1,3 +1,5 @@
 to supplement 'git add -u' behavior -- to add only updated (tracked only, no untracked) files to be committed.  ATM all files would be added, including untracked.
 
 [[!meta author=yoh]]
+
+> [[done]]
diff --git a/doc/todo/annex_add___40__-u__124__--update__41___mode/comment_1_bde2b1e2c45e110d56ce98b43dd77743._comment b/doc/todo/annex_add___40__-u__124__--update__41___mode/comment_1_bde2b1e2c45e110d56ce98b43dd77743._comment
new file mode 100644
index 000000000..e6a632902
--- /dev/null
+++ b/doc/todo/annex_add___40__-u__124__--update__41___mode/comment_1_bde2b1e2c45e110d56ce98b43dd77743._comment
@@ -0,0 +1,7 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2017-04-07T19:41:02Z"
+ content="""
+Good idea, adding.
+"""]]