got bash completion working for "git annex" not just "git-annex"

This needs a patch to git to cause the git-annex completion to be
auto-loaded when completing "git annex <tab>". Otherwise, it will only
load when "git-annex" is tab completed. Once loaded, it works for both
uses. I've submitted the git patch to the git mailing list.

Makefile

@@ -49,7 +49,7 @@ install: build install-docs Build/InstallDesktopFile
 	ln -sf git-annex $(DESTDIR)$(PREFIX)/bin/git-annex-shell
 	./Build/InstallDesktopFile $(PREFIX)/bin/git-annex || true
 	install -d $(DESTDIR)$(PREFIX)/share/bash-completion/completions
-	./git-annex --bash-completion-script git-annex > $(DESTDIR)$(PREFIX)/share/bash-completion/completions/git-annex
+	install -m 0644 bash-completion.bash $(DESTDIR)$(PREFIX)/share/bash-completion/completions/git-annex
 
 test: git-annex
 	./git-annex test

bash-completion.bash

@@ -0,0 +1,25 @@
+# Use git-annex's built-in bash completion
+# This bash completion is generated by the option parser, so it covers all
+# commands, all options, and will never go out of date!
+source <(git-annex --bash-completion-script git-annex)
+
+# Called by git's bash completion script when completing "git annex"
+_git_annex() {
+    local cmdline
+    CMDLINE=(--bash-completion-index $(($COMP_CWORD - 1)))
+
+    local seen_git
+    local seen_annex
+    for arg in ${COMP_WORDS[@]}; do
+        if [ "$arg" = git ] && [ -z "$seen_git" ]; then
+		seen_git=1
+		CMDLINE=(${CMDLINE[@]} --bash-completion-word git-annex)
+	elif [ "$arg" = annex ] && [ -z "$seen_annex" ]; then
+		seen_annex=1
+	else
+		CMDLINE=(${CMDLINE[@]} --bash-completion-word $arg)
+	fi
+    done
+
+    COMPREPLY=( $(git-annex "${CMDLINE[@]}") )
+}

doc/forum/bash_completion/comment_5_d45570fd750ae8d69dedc3edeef0cc10._comment

@@ -3,13 +3,11 @@
  subject="""comment 5"""
  date="2015-07-15T15:44:11Z"
  content="""
-I've recently added built-in bash completion to git-annex, which is output
+I've recently added built-in bash completion to git-annex, enabled by the
-by the `--bash-completion-script` option. It knows about all sub-commands,
+`bash-completion.bash` file. It knows about all sub-commands,
 and all options, and will automatically always be up-to-date with the
 argument parser!
 
 Currently, it only works for completing "git-annex", not "git annex".
-Supporting the latter would probably require some hacks to git's own bash
+I have submitted a patch to git's bash completion to make the latter work.
-completion code, or possibly a smart way to hook into it.. Help with that
-would be appreciated.
 """]]

doc/git-annex.mdwn

@@ -763,18 +763,6 @@ may not be explicitly listed on their individual man pages.
 
   Overrides git configuration settings. May be specified multiple times.
 
-# COMMAND-LINE TAB COMPLETION
-
-To enable bash completion, paste this into your shell prompt:
-
-	source <(git-annex --bash-completion-script git-annex)
-
-The output of "git-annex --bash-completion-script git-annex" can also
-be written to a bash completion file so bash loads it automatically.
-
-This bash completion is generated by the option parser, so it covers all
-commands, all options, and will never go out of date!
-
 # CONFIGURATION VIA .git/config
 
 Like other git commands, git-annex is configured via `.git/config`.