Microproject | Add more builtin patterns for userdiff

[Pickfire <pickfire@xxxxxxxxxx>]

While I was working buildins shell patterns for user diffs. I noticed that
the tests t4034 passes but I can reproduce it manually with:

    mkdir cpp/ && cd cpp/ && git init

    cat > pre <<EOF
    Foo():x(0&&1){}
    cout<<"Hello World!\n"<<endl;
    1 -1e10 0xabcdef 'x'
    [a] a->b a.b
    !a ~a a++ a-- 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 a!=b
    a&b
    a^b
    a|b
    a&&b
    a||b
    a?b:z
    a=b a+=b a-=b a*=b a/=b a%=b a<<=b a>>=b a&=b a^=b a|=b
    a,y
    a::b
    EOF

    cat > post <<EOF
    Foo() : x(0&42) { bar(x); }
    cout<<"Hello World?\n"<<endl;
    (1) (-1e10) (0xabcdef) 'y'
    [x] x->y x.y
    !x ~x x++ x-- 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
    x==y x!=y
    x&y
    x^y
    x|y
    x&&y
    x||y
    x?y:z
    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
    EOF

    echo '* diff="cpp"' > .gitmodules
    git diff --no-index --color-words pre post > output

Surprisingly, it shows (which is very different from the expected output):

^[[1mdiff --git a/pre b/post^[[m
^[[1mindex 23d5c8a..7e8c026 100644^[[m
^[[1m--- a/pre^[[m
^[[1m+++ b/post^[[m
^[[36m@@ -1,19 +1,19 @@^[[m
^[[31mFoo():x(0&&1){}^[[m^[[32mFoo() : x(0&42) { bar(x); }^[[m
cout<<"Hello ^[[31mWorld!\n"<<endl;^[[m
^[[31m1 -1e10 0xabcdef 'x'^[[m
^[[31m[a] a->b a.b^[[m
^[[31m!a ~a a++ a-- a*b a&b^[[m
^[[31ma*b a/b a%b^[[m
^[[31ma+b a-b^[[m
^[[31ma<<b a>>b^[[m
^[[31ma<b a<=b a>b a>=b^[[m
^[[31ma==b a!=b^[[m
^[[31ma&b^[[m
^[[31ma^b^[[m
^[[31ma|b^[[m
^[[31ma&&b^[[m
^[[31ma||b^[[m
^[[31ma?b:z^[[m
^[[31ma=b a+=b a-=b a*=b a/=b a%=b a<<=b a>>=b a&=b a^=b a|=b^[[m
^[[31ma,y^[[m
^[[31ma::b^[[m^[[32mWorld?\n"<<endl;^[[m
^[[32m(1) (-1e10) (0xabcdef) 'y'^[[m
^[[32m[x] x->y x.y^[[m
^[[32m!x ~x x++ x-- x*y x&y^[[m
^[[32mx*y x/y x%y^[[m
^[[32mx+y x-y^[[m
^[[32mx<<y x>>y^[[m
^[[32mx<y x<=y x>y x>=y^[[m
^[[32mx==y x!=y^[[m
^[[32mx&y^[[m
^[[32mx^y^[[m
^[[32mx|y^[[m
^[[32mx&&y^[[m
^[[32mx||y^[[m
^[[32mx?y:z^[[m
^[[32mx=y x+=y x-=y x*=y x/=y x%=y x<<=y x>>=y x&=y x^=y x|=y^[[m
^[[32mx,y^[[m
^[[32mx::y^[[m

Instead of:

<BOLD>diff --git a/pre b/post<RESET>
<BOLD>index 23d5c8a..7e8c026 100644<RESET>
<BOLD>--- a/pre<RESET>
<BOLD>+++ b/post<RESET>
<CYAN>@@ -1,19 +1,19 @@<RESET>
Foo() : x(0<RED>&&1<RESET><GREEN>&42<RESET>) { <GREEN>bar(x);<RESET> }
cout<<"Hello World<RED>!<RESET><GREEN>?<RESET>\n"<<endl;
<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<RESET><GREEN>x<RESET> ~<RED>a a<RESET><GREEN>x x<RESET>++ <RED>a<RESET><GREEN>x<RESET>-- <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>
<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<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<RESET>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>^<RED>b<RESET>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>|<RED>b<RESET>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>&&<RED>b<RESET>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>||<RED>b<RESET>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>?<RED>b<RESET><GREEN>y<RESET>:z
<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 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>
<RED>a<RESET><GREEN>y<RESET>
<GREEN>x<RESET>,y
<RED>a<RESET><GREEN>x<RESET>::<RED>b<RESET><GREEN>y<RESET>

That's does not just happens to cpp builtins, it happens to bibtex as well.
Is it that I had missed some configuration since I have tested this on a
few machines?

I have a workaround for that, which is to run log with --color-words=<regex>
with regex from the userdiff.c, does it automatically use the builtins diff?