[GSOC][PATCH] userdiff: Add JavaScript function patterns

[Sergius Nyah <sergiusnyah@gmail.com>]

This commit adds a patterns used to match JavaScript functions.
It now correctly identifies function declarations, function expressions,
and functions defined inside blocks. Add test for corresponding change in userdiff.

Signed-off-by: Sergius Nyah <sergiusnyah@gmail.com>
---
 t/t4018-diff-funcname.sh | 22 ++++++++++++++++++++++
 userdiff.c               | 12 ++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
index e026fac1f4..d35cce18a0 100755
--- a/t/t4018-diff-funcname.sh
+++ b/t/t4018-diff-funcname.sh
@@ -120,3 +120,25 @@ do
 done

 test_done
+
+test_expect_success 'identify builtin patterns in JavaScript' '
+	# setup
+	echo "function myFunction() { return true; }" > test.js &&
+	echo "var myVar = function() { return false; }" >> test.js &&
+	git add test.js &&
+	git commit -m "add test.js" &&
+
+	# modify the file
+	echo "function myFunction() { return false; }" > test.js &&
+	echo "var myVar = function() { return true; }" >> test.js &&
+
+	# command under test
+	git diff >output &&
+
+	# check results
+	test_i18ngrep "function myFunction() { return true; }" output &&
+	test_i18ngrep "function myFunction() { return false; }" output &&
+	test_i18ngrep "var myVar = function() { return false; }" output &&
+	test_i18ngrep "var myVar = function() { return true; }" output
+'
+test_done
\ No newline at end of file
diff --git a/userdiff.c b/userdiff.c
index 2b1dab2649..bbe2bcb9a3 100644
--- a/userdiff.c
+++ b/userdiff.c
+PATTERNS("javascript",
+      /* Looks for lines that start with optional whitespace, followed
+      * by 'function'* and any characters (for function declarations),
+      * or valid JavaScript identifiers, equals sign '=', 'function' keyword
+      * and any characters (for function expressions).
+      * Also considers functions defined inside blocks with '{...}'.
+      */
+      "^[ \t]*(function[ \t]*.*|[a-zA-Z_$][0-9a-zA-Z_$]*[ \t]*=[ \t]*function[ \t]*.*|(\\{[ \t]*)?)\n",
+      /* This pattern matches JavaScript identifiers */
+      "[a-zA-Z_$][0-9a-zA-Z_$]*"
+      "|[-+0-9.eE]+|0[xX][0-9a-fA-F]+"
+      "|[-+*/<>%&^|=!:]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\|"),
--
2.43.2