userdiff: add builtin diff driver for kotlin language.

The xfuncname pattern finds func/class declarations
in diffs to display as a hunk header. The word_regex
pattern finds individual tokens in Kotlin code to generate
appropriate diffs.

This patch adds xfuncname regex and word_regex for Kotlin
language.

Signed-off-by: Jaydeep P Das <jaydeepjd.8914@gmail.com>
Acked-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 103 insertions, 0 deletions

diff --git a/t/t4034/kotlin/expect b/t/t4034/kotlin/expect
new file mode 100644
index 0000000000..7f76f7540d
--- /dev/null
+++ b/t/t4034/kotlin/expect
@@ -0,0 +1,43 @@
+<BOLD>diff --git a/pre b/post<RESET>
+<BOLD>index 11ea3de..2e1df4c 100644<RESET>
+<BOLD>--- a/pre<RESET>
+<BOLD>+++ b/post<RESET>
+<CYAN>@@ -1,30 +1,30 @@<RESET>
+println("Hello World<RED>!\n<RESET><GREEN>?<RESET>")
+<GREEN>(<RESET>1<GREEN>) (<RESET>-1e10<GREEN>) (<RESET>0xabcdef<GREEN>)<RESET> '<RED>x<RESET><GREEN>y<RESET>'
+[<RED>a<RESET><GREEN>x<RESET>] <RED>a<RESET><GREEN>x<RESET>-><RED>b a<RESET><GREEN>y x<RESET>.<RED>b<RESET><GREEN>y<RESET>
+!<RED>a a<RESET><GREEN>x x<RESET>.inv() <RED>a<RESET><GREEN>x<RESET>*<RED>b a<RESET><GREEN>y x<RESET>&<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>*<RED>b a<RESET><GREEN>y x<RESET>/<RED>b a<RESET><GREEN>y x<RESET>%<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>+<RED>b a<RESET><GREEN>y x<RESET>-<RED>b<RESET><GREEN>y<RESET>
+a <RED>shr<RESET><GREEN>shl<RESET> b
+<RED>a<RESET><GREEN>x<RESET><<RED>b a<RESET><GREEN>y x<RESET><=<RED>b a<RESET><GREEN>y x<RESET>><RED>b a<RESET><GREEN>y x<RESET>>=<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>==<RED>b a<RESET><GREEN>y x<RESET>!=<RED>b a<RESET><GREEN>y x<RESET>===<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET> and <RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>^<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET> or <RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>&&<RED>b a<RESET><GREEN>y x<RESET>||<RED>b<RESET>
+<RED>a<RESET><GREEN>y<RESET>
+<GREEN>x<RESET>=<RED>b a<RESET><GREEN>y x<RESET>+=<RED>b a<RESET><GREEN>y x<RESET>-=<RED>b a<RESET><GREEN>y x<RESET>*=<RED>b a<RESET><GREEN>y x<RESET>/=<RED>b a<RESET><GREEN>y x<RESET>%=<RED>b a<RESET><GREEN>y x<RESET><<=<RED>b a<RESET><GREEN>y x<RESET>>>=<RED>b a<RESET><GREEN>y x<RESET>&=<RED>b a<RESET><GREEN>y x<RESET>^=<RED>b a<RESET><GREEN>y x<RESET>|=<RED>b<RESET><GREEN>y<RESET>
+a<RED>=<RESET><GREEN>+=<RESET>b c<RED>+=<RESET><GREEN>=<RESET>d e<RED>-=<RESET><GREEN><=<RESET>f g<RED>*=<RESET><GREEN>>=<RESET>h i<RED>/=<RESET><GREEN>/<RESET>j k<RED>%=<RESET><GREEN>%<RESET>l m<RED><<=<RESET><GREEN><<<RESET>n o<RED>>>=<RESET><GREEN>>><RESET>p q<RED>&=<RESET><GREEN>&<RESET>r s<RED>^=<RESET><GREEN>^<RESET>t u<RED>|=<RESET><GREEN>|<RESET>v
+a<RED><<=<RESET><GREEN><=<RESET>b
+a<RED>||<RESET><GREEN>|<RESET>b a<RED>&&<RESET><GREEN>&<RESET>b
+<RED>a<RESET><GREEN>x<RESET>,y
+--a<RED>==<RESET><GREEN>!=<RESET>--b
+a++<RED>==<RESET><GREEN>!=<RESET>++b
+<RED>0xFF_EC_DE_5E 0b100_000 100_000<RESET><GREEN>0xFF_E1_DE_5E 0b100_100 200_000<RESET>
+a<RED>==<RESET><GREEN>===<RESET>b
+a<RED>!!<RESET><GREEN>!=<RESET>b
+<RED>_32<RESET><GREEN>_33<RESET>.find(arr)
+X.<RED>fill<RESET><GREEN>find<RESET>()
+X.<RED>u<RESET><GREEN>f<RESET>+1
+X.u<RED>-<RESET><GREEN>+<RESET>2
+a<RED>.<RESET><GREEN>..<RESET>b
+a<RED>?.<RESET><GREEN>?:<RESET>b
+<RED>.32_00_456<RESET><GREEN>.32_00_446<RESET>
diff --git a/t/t4034/kotlin/post b/t/t4034/kotlin/post
new file mode 100644
index 0000000000..2e1df4c6d5
--- /dev/null
+++ b/t/t4034/kotlin/post
@@ -0,0 +1,30 @@
+println("Hello World?")
+(1) (-1e10) (0xabcdef) 'y'
+[x] x->y x.y
+!x x.inv() x*y x&y
+x*y x/y x%y
+x+y x-y
+a shl b
+x<y x<=y x>y x>=y
+x==y x!=y x===y
+x and y
+x^y
+x or y
+x&&y x||y
+x=y x+=y x-=y x*=y x/=y x%=y x<<=y x>>=y x&=y x^=y x|=y
+a+=b c=d e<=f g>=h i/j k%l m<<n o>>p q&r s^t u|v
+a<=b
+a|b a&b
+x,y
+--a!=--b
+a++!=++b
+0xFF_E1_DE_5E 0b100_100 200_000
+a===b
+a!=b
+_33.find(arr)
+X.find()
+X.f+1
+X.u+2
+a..b
+a?:b
+.32_00_446
diff --git a/t/t4034/kotlin/pre b/t/t4034/kotlin/pre
new file mode 100644
index 0000000000..11ea3de665
--- /dev/null
+++ b/t/t4034/kotlin/pre
@@ -0,0 +1,30 @@
+println("Hello World!\n")
+1 -1e10 0xabcdef 'x'
+[a] a->b a.b
+!a a.inv() a*b a&b
+a*b a/b a%b
+a+b a-b
+a shr b
+a<b a<=b a>b a>=b
+a==b a!=b a===b
+a and b
+a^b
+a or b
+a&&b a||b
+a=b a+=b a-=b a*=b a/=b a%=b a<<=b a>>=b a&=b a^=b a|=b
+a=b c+=d e-=f g*=h i/=j k%=l m<<=n o>>=p q&=r s^=t u|=v
+a<<=b
+a||b a&&b
+a,y
+--a==--b
+a++==++b
+0xFF_EC_DE_5E 0b100_000 100_000
+a==b
+a!!b
+_32.find(arr)
+X.fill()
+X.u+1
+X.u-2
+a.b
+a?.b
+.32_00_456