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/coffee.go

@@ -0,0 +1,91 @@
+package c
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Coffeescript lexer.
+var Coffeescript = internal.Register(MustNewLexer(
+	&Config{
+		Name:         "CoffeeScript",
+		Aliases:      []string{"coffee-script", "coffeescript", "coffee"},
+		Filenames:    []string{"*.coffee"},
+		MimeTypes:    []string{"text/coffeescript"},
+		NotMultiline: true,
+		DotAll:       true,
+	},
+	Rules{
+		"commentsandwhitespace": {
+			{`\s+`, Text, nil},
+			{`###[^#].*?###`, CommentMultiline, nil},
+			{`#(?!##[^#]).*?\n`, CommentSingle, nil},
+		},
+		"multilineregex": {
+			{`[^/#]+`, LiteralStringRegex, nil},
+			{`///([gim]+\b|\B)`, LiteralStringRegex, Pop(1)},
+			{`#\{`, LiteralStringInterpol, Push("interpoling_string")},
+			{`[/#]`, LiteralStringRegex, nil},
+		},
+		"slashstartsregex": {
+			Include("commentsandwhitespace"),
+			{`///`, LiteralStringRegex, Push("#pop", "multilineregex")},
+			{`/(?! )(\\.|[^[/\\\n]|\[(\\.|[^\]\\\n])*])+/([gim]+\b|\B)`, LiteralStringRegex, Pop(1)},
+			{`/`, Operator, nil},
+			Default(Pop(1)),
+		},
+		"root": {
+			Include("commentsandwhitespace"),
+			{`^(?=\s|/)`, Text, Push("slashstartsregex")},
+			{"\\+\\+|~|&&|\\band\\b|\\bor\\b|\\bis\\b|\\bisnt\\b|\\bnot\\b|\\?|:|\\|\\||\\\\(?=\\n)|(<<|>>>?|==?(?!>)|!=?|=(?!>)|-(?!>)|[<>+*`%&\\|\\^/])=?", Operator, Push("slashstartsregex")},
+			{`(?:\([^()]*\))?\s*[=-]>`, NameFunction, Push("slashstartsregex")},
+			{`[{(\[;,]`, Punctuation, Push("slashstartsregex")},
+			{`[})\].]`, Punctuation, nil},
+			{`(?<![.$])(for|own|in|of|while|until|loop|break|return|continue|switch|when|then|if|unless|else|throw|try|catch|finally|new|delete|typeof|instanceof|super|extends|this|class|by)\b`, Keyword, Push("slashstartsregex")},
+			{`(?<![.$])(true|false|yes|no|on|off|null|NaN|Infinity|undefined)\b`, KeywordConstant, nil},
+			{`(Array|Boolean|Date|Error|Function|Math|netscape|Number|Object|Packages|RegExp|String|sun|decodeURI|decodeURIComponent|encodeURI|encodeURIComponent|eval|isFinite|isNaN|parseFloat|parseInt|document|window)\b`, NameBuiltin, nil},
+			{`[$a-zA-Z_][\w.:$]*\s*[:=]\s`, NameVariable, Push("slashstartsregex")},
+			{`@[$a-zA-Z_][\w.:$]*\s*[:=]\s`, NameVariableInstance, Push("slashstartsregex")},
+			{`@`, NameOther, Push("slashstartsregex")},
+			{`@?[$a-zA-Z_][\w$]*`, NameOther, nil},
+			{`[0-9][0-9]*\.[0-9]+([eE][0-9]+)?[fd]?`, LiteralNumberFloat, nil},
+			{`0x[0-9a-fA-F]+`, LiteralNumberHex, nil},
+			{`[0-9]+`, LiteralNumberInteger, nil},
+			{`"""`, LiteralString, Push("tdqs")},
+			{`'''`, LiteralString, Push("tsqs")},
+			{`"`, LiteralString, Push("dqs")},
+			{`'`, LiteralString, Push("sqs")},
+		},
+		"strings": {
+			{`[^#\\\'"]+`, LiteralString, nil},
+		},
+		"interpoling_string": {
+			{`\}`, LiteralStringInterpol, Pop(1)},
+			Include("root"),
+		},
+		"dqs": {
+			{`"`, LiteralString, Pop(1)},
+			{`\\.|\'`, LiteralString, nil},
+			{`#\{`, LiteralStringInterpol, Push("interpoling_string")},
+			{`#`, LiteralString, nil},
+			Include("strings"),
+		},
+		"sqs": {
+			{`'`, LiteralString, Pop(1)},
+			{`#|\\.|"`, LiteralString, nil},
+			Include("strings"),
+		},
+		"tdqs": {
+			{`"""`, LiteralString, Pop(1)},
+			{`\\.|\'|"`, LiteralString, nil},
+			{`#\{`, LiteralStringInterpol, Push("interpoling_string")},
+			{`#`, LiteralString, nil},
+			Include("strings"),
+		},
+		"tsqs": {
+			{`'''`, LiteralString, Pop(1)},
+			{`#|\\.|\'|"`, LiteralString, nil},
+			Include("strings"),
+		},
+	},
+))