[PATCH] completion: Handle '!f() { ... }; f' aliases

[Steffen Prohaska <prohaska@zib.de>]

'!f() { ... }; f' is a recommended pattern to declare more complex
aliases (see git wiki [1]).  This commit teaches the completion to
handle them.

When determining which completion to use for an alias, the opening brace
is now ignored in order to continue the search for a git command inside
the function body.  For example, the alias '!f() { git commit ... }' now
triggers commit completion.  Previously, the search stopped on '{', and
the completion tried it to determine how to complete, which obviously
was useless.

Furthermore, the null command ':' is now skipped, so that it can be used
as a workaround to declare the desired completion style.  For example,
the alias '!f() { : git commit ; if ...  ' now triggers commit
completion.

[1] https://git.wiki.kernel.org/index.php/Aliases

Signed-off-by: Steffen Prohaska <prohaska@zib.de>
---
 contrib/completion/git-completion.bash |  7 +++++++
 t/t9902-completion.sh                  | 20 ++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 2c59a76..aecb975 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -21,6 +21,11 @@
 #        source ~/.git-completion.sh
 #    3) Consider changing your PS1 to also show the current branch,
 #       see git-prompt.sh for details.
+#
+# If you use complex aliases of form '!f() { ... }; f', you can use the null
+# command ':' as the first command in the function body to declare the desired
+# completion style.  For example '!f() { : git commit ; ... }; f' will
+# tell the completion to use commit completion.
 
 case "$COMP_WORDBREAKS" in
 *:*) : great ;;
@@ -781,6 +786,8 @@ __git_aliased_command ()
 		-*)	: option ;;
 		*=*)	: setting env ;;
 		git)	: git itself ;;
+		{)	: skip start of shell helper function ;;
+		:)	: skip null command ;;
 		*)
 			echo "$word"
 			return
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 2d4beb5..ea48681 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -550,6 +550,26 @@ test_expect_success 'complete files' '
 	test_completion "git add mom" "momified"
 '
 
+test_expect_success 'completion uses <cmd> completion for alias !f() { VAR=val git <cmd> ... }' '
+	git config alias.co "!f() { VAR=val git checkout ... ; } f" &&
+	test_completion "git co m" <<-\EOF &&
+	master Z
+	mybranch Z
+	mytag Z
+	EOF
+	git config --unset alias.co
+'
+
+test_expect_success 'completion used <cmd> completion for alias !f() { : git <cmd> ; ... }' '
+	git config alias.co "!f() { : git checkout ; if ... } f" &&
+	test_completion "git co m" <<-\EOF &&
+	master Z
+	mybranch Z
+	mytag Z
+	EOF
+	git config --unset alias.co
+'
+
 test_expect_failure 'complete with tilde expansion' '
 	git init tmp && cd tmp &&
 	test_when_finished "cd .. && rm -rf tmp" &&
-- 
2.0.0.244.g4e8e734