merge: Support --json and --json-error-messages and --json-progress

Seems unlikely to be very useful, but trivial.
And, this completes the story that git-annex sync does not need json,
since every sub-operation is available in a command that does support json.
(Well, except for committing, but that's not a git-annex command.)

Sponsored-By: the NIH-funded NICEMAN (ReproNim TR&D3) project

CHANGELOG

@@ -39,8 +39,8 @@ git-annex (10.20230408) UNRELEASED; urgency=medium
     broken.
   * Support --json and --json-error-messages in more commands
     (addunused, dead, describe, dropunused, expire, fix, importfeed, init,
-    log, migrate, reinit, reinject, rekey, renameremote, rmurl, semitrust,
-    setpresentkey, trust, unannex, undo, untrust, unused)
+    log, merge, migrate, reinit, reinject, rekey, renameremote, rmurl,
+    semitrust, setpresentkey, trust, unannex, undo, untrust, unused)
   * log: When --raw-date is used, display only seconds from the epoch, as
     documented, omitting a trailing "s" that was included in the output
     before.

Command/Merge.hs

@@ -16,9 +16,10 @@ import Command.Sync (prepMerge, mergeLocal, mergeConfig, merge, notOnlyAnnexOpti
 import Git.Types
 
 cmd :: Command
-cmd = command "merge" SectionMaintenance
-	"merge changes from remotes"
-	(paramOptional paramRef) (seek <$$> optParser)
+cmd = withAnnexOptions [jsonOptions] $
+	command "merge" SectionMaintenance
+		"merge changes from remotes"
+		(paramOptional paramRef) (seek <$$> optParser)
 
 data MergeOptions = MergeOptions
 	{ mergeBranches :: [String]

doc/git-annex-merge.mdwn

@@ -27,6 +27,16 @@ will not be done.
   Passed on to `git merge`, to control whether or not to merge
   histories that do not share a common ancestor.
 
+* `--json`
+
+  Enable JSON output. This is intended to be parsed by programs that use
+  git-annex. Each line of output is a JSON object.
+
+* `--json-error-messages`
+
+  Messages that would normally be output to standard error are included in
+  the JSON instead.
+
 * Also, the [[git-annex-common-options]](1) can be used.
 
 # SEE ALSO

doc/todo/--json_for_unannex__and_ideally_any_other_command_.mdwn

@@ -37,15 +37,13 @@ These commands have been updated to support --json:
 * git-annex-reinject
 * git-annex-renameremote
 * git-annex-importfeed
+* git-annex-merge
 
 Provisional list of commands that don't support --json and maybe should:
 
-(Feel free to reorder things to the top)
-
 * git-annex-configremote
 * git-annex-enableremote
 * git-annex-initremote
-* git-annex-merge
 * git-annex-upgrade
 
 These commands could support json, but I punted: