Server-side syntax highlighting for all code (#12047)

* Server-side syntax hilighting for all code

This PR does a few things:

* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green

Fixes #7729
Fixes #10157
Fixes #11825
Fixes #7728
Fixes #3872
Fixes #3682

And perhaps gets closer to #9553

* fix line marker

* fix repo search

* Fix single line select

* properly load settings

* npm uninstall highlight.js

* review suggestion

* code review

* forgot to call function

* fix test

* Apply suggestions from code review

suggestions from @silverwind thanks

Co-authored-by: silverwind <me@silverwind.io>

* code review

* copy/paste error

* Use const for highlight size limit

* Update web_src/less/_repository.less

Co-authored-by: Lauris BH <lauris@nix.lv>

* update size limit to 1MB and other styling tweaks

* fix highlighting for certain diff sections

* fix test

* add worker back as suggested

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/alecthomas/chroma/lexers/c/c.go

@@ -0,0 +1,91 @@
+package c
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// C lexer.
+var C = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "C",
+		Aliases:   []string{"c"},
+		Filenames: []string{"*.c", "*.h", "*.idc"},
+		MimeTypes: []string{"text/x-chdr", "text/x-csrc"},
+	},
+	Rules{
+		"whitespace": {
+			{`^#if\s+0`, CommentPreproc, Push("if0")},
+			{`^#`, CommentPreproc, Push("macro")},
+			{`^(\s*(?:/[*].*?[*]/\s*)?)(#if\s+0)`, ByGroups(UsingSelf("root"), CommentPreproc), Push("if0")},
+			{`^(\s*(?:/[*].*?[*]/\s*)?)(#)`, ByGroups(UsingSelf("root"), CommentPreproc), Push("macro")},
+			{`\n`, Text, nil},
+			{`\s+`, Text, nil},
+			{`\\\n`, Text, nil},
+			{`//(\n|[\w\W]*?[^\\]\n)`, CommentSingle, nil},
+			{`/(\\\n)?[*][\w\W]*?[*](\\\n)?/`, CommentMultiline, nil},
+			{`/(\\\n)?[*][\w\W]*`, CommentMultiline, nil},
+		},
+		"statements": {
+			{`(L?)(")`, ByGroups(LiteralStringAffix, LiteralString), Push("string")},
+			{`(L?)(')(\\.|\\[0-7]{1,3}|\\x[a-fA-F0-9]{1,2}|[^\\\'\n])(')`, ByGroups(LiteralStringAffix, LiteralStringChar, LiteralStringChar, LiteralStringChar), nil},
+			{`(\d+\.\d*|\.\d+|\d+)[eE][+-]?\d+[LlUu]*`, LiteralNumberFloat, nil},
+			{`(\d+\.\d*|\.\d+|\d+[fF])[fF]?`, LiteralNumberFloat, nil},
+			{`0x[0-9a-fA-F]+[LlUu]*`, LiteralNumberHex, nil},
+			{`0[0-7]+[LlUu]*`, LiteralNumberOct, nil},
+			{`\d+[LlUu]*`, LiteralNumberInteger, nil},
+			{`\*/`, Error, nil},
+			{`[~!%^&*+=|?:<>/-]`, Operator, nil},
+			{`[()\[\],.]`, Punctuation, nil},
+			{Words(``, `\b`, `asm`, `auto`, `break`, `case`, `const`, `continue`, `default`, `do`, `else`, `enum`, `extern`, `for`, `goto`, `if`, `register`, `restricted`, `return`, `sizeof`, `static`, `struct`, `switch`, `typedef`, `union`, `volatile`, `while`), Keyword, nil},
+			{`(bool|int|long|float|short|double|char|unsigned|signed|void)\b`, KeywordType, nil},
+			{Words(``, `\b`, `inline`, `_inline`, `__inline`, `naked`, `restrict`, `thread`, `typename`), KeywordReserved, nil},
+			{`(__m(128i|128d|128|64))\b`, KeywordReserved, nil},
+			{Words(`__`, `\b`, `asm`, `int8`, `based`, `except`, `int16`, `stdcall`, `cdecl`, `fastcall`, `int32`, `declspec`, `finally`, `int64`, `try`, `leave`, `wchar_t`, `w64`, `unaligned`, `raise`, `noop`, `identifier`, `forceinline`, `assume`), KeywordReserved, nil},
+			{`(true|false|NULL)\b`, NameBuiltin, nil},
+			{`([a-zA-Z_]\w*)(\s*)(:)(?!:)`, ByGroups(NameLabel, Text, Punctuation), nil},
+			{`[a-zA-Z_]\w*`, Name, nil},
+		},
+		"root": {
+			Include("whitespace"),
+			{`((?:[\w*\s])+?(?:\s|[*]))([a-zA-Z_]\w*)(\s*\([^;]*?\))([^;{]*)(\{)`, ByGroups(UsingSelf("root"), NameFunction, UsingSelf("root"), UsingSelf("root"), Punctuation), Push("function")},
+			{`((?:[\w*\s])+?(?:\s|[*]))([a-zA-Z_]\w*)(\s*\([^;]*?\))([^;]*)(;)`, ByGroups(UsingSelf("root"), NameFunction, UsingSelf("root"), UsingSelf("root"), Punctuation), nil},
+			Default(Push("statement")),
+		},
+		"statement": {
+			Include("whitespace"),
+			Include("statements"),
+			{`[{}]`, Punctuation, nil},
+			{`;`, Punctuation, Pop(1)},
+		},
+		"function": {
+			Include("whitespace"),
+			Include("statements"),
+			{`;`, Punctuation, nil},
+			{`\{`, Punctuation, Push()},
+			{`\}`, Punctuation, Pop(1)},
+		},
+		"string": {
+			{`"`, LiteralString, Pop(1)},
+			{`\\([\\abfnrtv"\']|x[a-fA-F0-9]{2,4}|u[a-fA-F0-9]{4}|U[a-fA-F0-9]{8}|[0-7]{1,3})`, LiteralStringEscape, nil},
+			{`[^\\"\n]+`, LiteralString, nil},
+			{`\\\n`, LiteralString, nil},
+			{`\\`, LiteralString, nil},
+		},
+		"macro": {
+			{`(include)(\s*(?:/[*].*?[*]/\s*)?)([^\n]+)`, ByGroups(CommentPreproc, Text, CommentPreprocFile), nil},
+			{`[^/\n]+`, CommentPreproc, nil},
+			{`/[*](.|\n)*?[*]/`, CommentMultiline, nil},
+			{`//.*?\n`, CommentSingle, Pop(1)},
+			{`/`, CommentPreproc, nil},
+			{`(?<=\\)\n`, CommentPreproc, nil},
+			{`\n`, CommentPreproc, Pop(1)},
+		},
+		"if0": {
+			{`^\s*#if.*?(?<!\\)\n`, CommentPreproc, Push()},
+			{`^\s*#el(?:se|if).*\n`, CommentPreproc, Pop(1)},
+			{`^\s*#endif.*?(?<!\\)\n`, CommentPreproc, Pop(1)},
+			{`.*?\n`, Comment, nil},
+		},
+	},
+))