diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 2d0a03715b..8a15ff6bdf 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -802,6 +802,8 @@ patterns are available:
 
 - `ada` suitable for source code in the Ada language.
 
+- `bash` suitable for source code in the Bourne-Again SHell language.
+
 - `bibtex` suitable for files with BibTeX coded references.
 
 - `cpp` suitable for source code in the C and C++ languages.
diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
index 9d07797579..d18c4669d2 100755
--- a/t/t4018-diff-funcname.sh
+++ b/t/t4018-diff-funcname.sh
@@ -27,6 +27,7 @@ test_expect_success 'setup' '
 
 diffpatterns="
 	ada
+	bash
 	bibtex
 	cpp
 	csharp
@@ -106,10 +107,19 @@ do
 	else
 		result=success
 	fi
-	test_expect_$result "hunk header: $i" "
-		git diff -U1 $i >actual &&
-		grep '@@ .* @@.*RIGHT' actual
-	"
+
+	if grep non-match "$i" >/dev/null 2>&1
+	then
+		test_expect_$result "hunk header non-match: $i" "
+			git diff -U1 $i >actual &&
+			! grep '@@ .* @@.*RIGHT' actual
+		"
+	else
+		test_expect_$result "hunk header: $i" "
+			git diff -U1 $i >actual &&
+			grep '@@ .* @@.*RIGHT' actual
+		"
+	fi
 done
 
 test_done
diff --git a/t/t4018/README b/t/t4018/README
index 283e01cca1..cfe2b86ee7 100644
--- a/t/t4018/README
+++ b/t/t4018/README
@@ -10,6 +10,9 @@ The text that must appear in the hunk header must contain the word
 To mark a test case that highlights a malfunction, insert the word
 BROKEN in all lower-case somewhere in the file.
 
+To mark a test case that verifies some text is not matched, insert the
+word NON-MATCH in all lower-case somewhere in the file.
+
 This text is a bit twisted and out of order, but it is itself a
 test case for the default hunk header pattern. Know what you are doing
 if you change it.
diff --git a/t/t4018/bash-arithmetic-function b/t/t4018/bash-arithmetic-function
new file mode 100644
index 0000000000..c0b276cb50
--- /dev/null
+++ b/t/t4018/bash-arithmetic-function
@@ -0,0 +1,4 @@
+RIGHT() ((
+
+    ChangeMe = "$x" + "$y"
+))
diff --git a/t/t4018/bash-bashism-style-compact b/t/t4018/bash-bashism-style-compact
new file mode 100644
index 0000000000..9a06bb08fd
--- /dev/null
+++ b/t/t4018/bash-bashism-style-compact
@@ -0,0 +1,4 @@
+function RIGHT{ # non-match
+    :
+    echo 'ChangeMe'
+}
diff --git a/t/t4018/bash-bashism-style-function b/t/t4018/bash-bashism-style-function
new file mode 100644
index 0000000000..f1de4fa831
--- /dev/null
+++ b/t/t4018/bash-bashism-style-function
@@ -0,0 +1,4 @@
+function RIGHT {
+    :
+    echo 'ChangeMe'
+}
diff --git a/t/t4018/bash-bashism-style-whitespace b/t/t4018/bash-bashism-style-whitespace
new file mode 100644
index 0000000000..ade85dd3a5
--- /dev/null
+++ b/t/t4018/bash-bashism-style-whitespace
@@ -0,0 +1,4 @@
+	 function 	RIGHT 	( 	) 	{
+
+	    ChangeMe
+	 }
diff --git a/t/t4018/bash-conditional-function b/t/t4018/bash-conditional-function
new file mode 100644
index 0000000000..c5949e829b
--- /dev/null
+++ b/t/t4018/bash-conditional-function
@@ -0,0 +1,4 @@
+RIGHT() [[ \
+
+    "$a" > "$ChangeMe"
+]]
diff --git a/t/t4018/bash-missing-parentheses b/t/t4018/bash-missing-parentheses
new file mode 100644
index 0000000000..d112761300
--- /dev/null
+++ b/t/t4018/bash-missing-parentheses
@@ -0,0 +1,4 @@
+functionRIGHT { # non-match
+    :
+    echo 'ChangeMe'
+}
diff --git a/t/t4018/bash-mixed-style-compact b/t/t4018/bash-mixed-style-compact
new file mode 100644
index 0000000000..d9364cba67
--- /dev/null
+++ b/t/t4018/bash-mixed-style-compact
@@ -0,0 +1,4 @@
+function RIGHT(){
+    :
+    echo 'ChangeMe'
+}
diff --git a/t/t4018/bash-mixed-style-function b/t/t4018/bash-mixed-style-function
new file mode 100644
index 0000000000..555f9b2466
--- /dev/null
+++ b/t/t4018/bash-mixed-style-function
@@ -0,0 +1,4 @@
+function RIGHT() {
+
+    ChangeMe
+}
diff --git a/t/t4018/bash-other-characters b/t/t4018/bash-other-characters
new file mode 100644
index 0000000000..a3f390d525
--- /dev/null
+++ b/t/t4018/bash-other-characters
@@ -0,0 +1,4 @@
+_RIGHT_0n() {
+
+    ChangeMe
+}
diff --git a/t/t4018/bash-posix-style-compact b/t/t4018/bash-posix-style-compact
new file mode 100644
index 0000000000..045bd2029b
--- /dev/null
+++ b/t/t4018/bash-posix-style-compact
@@ -0,0 +1,4 @@
+RIGHT(){
+
+    ChangeMe
+}
diff --git a/t/t4018/bash-posix-style-function b/t/t4018/bash-posix-style-function
new file mode 100644
index 0000000000..a4d144856e
--- /dev/null
+++ b/t/t4018/bash-posix-style-function
@@ -0,0 +1,4 @@
+RIGHT() {
+
+    ChangeMe
+}
diff --git a/t/t4018/bash-posix-style-whitespace b/t/t4018/bash-posix-style-whitespace
new file mode 100644
index 0000000000..4d984f0aa4
--- /dev/null
+++ b/t/t4018/bash-posix-style-whitespace
@@ -0,0 +1,4 @@
+	 RIGHT 	( 	) 	{
+
+	    ChangeMe
+	 }
diff --git a/t/t4018/bash-subshell-function b/t/t4018/bash-subshell-function
new file mode 100644
index 0000000000..80baa09484
--- /dev/null
+++ b/t/t4018/bash-subshell-function
@@ -0,0 +1,4 @@
+RIGHT() (
+
+    ChangeMe=2
+)
diff --git a/t/t4018/bash-trailing-comment b/t/t4018/bash-trailing-comment
new file mode 100644
index 0000000000..f1edbeda31
--- /dev/null
+++ b/t/t4018/bash-trailing-comment
@@ -0,0 +1,4 @@
+RIGHT() { # Comment
+
+    ChangeMe
+}
diff --git a/userdiff.c b/userdiff.c
index fde02f225b..8830019f05 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -23,6 +23,28 @@ IPATTERN("ada",
 	 "[a-zA-Z][a-zA-Z0-9_]*"
 	 "|[-+]?[0-9][0-9#_.aAbBcCdDeEfF]*([eE][+-]?[0-9_]+)?"
 	 "|=>|\\.\\.|\\*\\*|:=|/=|>=|<=|<<|>>|<>"),
+PATTERNS("bash",
+	 /* Optional leading indentation */
+	 "^[ \t]*"
+	 /* Start of function definition */
+	 "("
+	 /* Start of POSIX/Bashism grouping */
+	 "("
+	 /* POSIX identifier with mandatory parentheses */
+	 "[a-zA-Z_][a-zA-Z0-9_]*[ \t]*\\([ \t]*\\))"
+	 /* Bashism identifier with optional parentheses */
+	 "|(function[ \t]+[a-zA-Z_][a-zA-Z0-9_]*(([ \t]*\\([ \t]*\\))|([ \t]+))"
+	 /* End of POSIX/Bashism grouping */
+	 ")"
+	 /* Optional whitespace */
+	 "[ \t]*"
+	 /* Compound command starting with `{`, `(`, `((` or `[[` */
+	 "(\\{|\\(\\(?|\\[\\[)"
+	 /* End of function definition */
+	 ")",
+	 /* -- */
+	 /* Characters not in the default $IFS value */
+	 "[^ \t]+"),
 PATTERNS("dts",
 	 "!;\n"
 	 "!=\n"
