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/circular/doc.go

@@ -0,0 +1,2 @@
+// Package circular exists to break circular dependencies between lexers.
+package circular

vendor/github.com/alecthomas/chroma/lexers/circular/php.go

@@ -0,0 +1,91 @@
+package circular
+
+import (
+	"strings"
+
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/h"
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// PHP lexer.
+var PHP = internal.Register(DelegatingLexer(h.HTML, MustNewLexer(
+	&Config{
+		Name:            "PHP",
+		Aliases:         []string{"php", "php3", "php4", "php5"},
+		Filenames:       []string{"*.php", "*.php[345]", "*.inc"},
+		MimeTypes:       []string{"text/x-php"},
+		DotAll:          true,
+		CaseInsensitive: true,
+		EnsureNL:        true,
+	},
+	Rules{
+		"root": {
+			{`<\?(php)?`, CommentPreproc, Push("php")},
+			{`[^<]+`, Other, nil},
+			{`<`, Other, nil},
+		},
+		"php": {
+			{`\?>`, CommentPreproc, Pop(1)},
+			{`(<<<)([\'"]?)((?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*)(\2\n.*?\n\s*)(\3)(;?)(\n)`, ByGroups(LiteralString, LiteralString, LiteralStringDelimiter, LiteralString, LiteralStringDelimiter, Punctuation, Text), nil},
+			{`\s+`, Text, nil},
+			{`#.*?\n`, CommentSingle, nil},
+			{`//.*?\n`, CommentSingle, nil},
+			{`/\*\*/`, CommentMultiline, nil},
+			{`/\*\*.*?\*/`, LiteralStringDoc, nil},
+			{`/\*.*?\*/`, CommentMultiline, nil},
+			{`(->|::)(\s*)((?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*)`, ByGroups(Operator, Text, NameAttribute), nil},
+			{`[~!%^&*+=|:.<>/@-]+`, Operator, nil},
+			{`\?`, Operator, nil},
+			{`[\[\]{}();,]+`, Punctuation, nil},
+			{`(class)(\s+)`, ByGroups(Keyword, Text), Push("classname")},
+			{`(function)(\s*)(?=\()`, ByGroups(Keyword, Text), nil},
+			{`(function)(\s+)(&?)(\s*)`, ByGroups(Keyword, Text, Operator, Text), Push("functionname")},
+			{`(const)(\s+)((?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*)`, ByGroups(Keyword, Text, NameConstant), nil},
+			{`(and|E_PARSE|old_function|E_ERROR|or|as|E_WARNING|parent|eval|PHP_OS|break|exit|case|extends|PHP_VERSION|cfunction|FALSE|print|for|require|continue|foreach|require_once|declare|return|default|static|do|switch|die|stdClass|echo|else|TRUE|elseif|var|empty|if|xor|enddeclare|include|virtual|endfor|include_once|while|endforeach|global|endif|list|endswitch|new|endwhile|not|array|E_ALL|NULL|final|php_user_filter|interface|implements|public|private|protected|abstract|clone|try|catch|throw|this|use|namespace|trait|yield|finally)\b`, Keyword, nil},
+			{`(true|false|null)\b`, KeywordConstant, nil},
+			Include("magicconstants"),
+			{`\$\{\$+(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*\}`, NameVariable, nil},
+			{`\$+(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*`, NameVariable, nil},
+			{`(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*`, NameOther, nil},
+			{`(\d+\.\d*|\d*\.\d+)(e[+-]?[0-9]+)?`, LiteralNumberFloat, nil},
+			{`\d+e[+-]?[0-9]+`, LiteralNumberFloat, nil},
+			{`0[0-7]+`, LiteralNumberOct, nil},
+			{`0x[a-f0-9]+`, LiteralNumberHex, nil},
+			{`\d+`, LiteralNumberInteger, nil},
+			{`0b[01]+`, LiteralNumberBin, nil},
+			{`'([^'\\]*(?:\\.[^'\\]*)*)'`, LiteralStringSingle, nil},
+			{"`([^`\\\\]*(?:\\\\.[^`\\\\]*)*)`", LiteralStringBacktick, nil},
+			{`"`, LiteralStringDouble, Push("string")},
+		},
+		"magicfuncs": {
+			{Words(``, `\b`, `__construct`, `__destruct`, `__call`, `__callStatic`, `__get`, `__set`, `__isset`, `__unset`, `__sleep`, `__wakeup`, `__toString`, `__invoke`, `__set_state`, `__clone`, `__debugInfo`), NameFunctionMagic, nil},
+		},
+		"magicconstants": {
+			{Words(``, `\b`, `__LINE__`, `__FILE__`, `__DIR__`, `__FUNCTION__`, `__CLASS__`, `__TRAIT__`, `__METHOD__`, `__NAMESPACE__`), NameConstant, nil},
+		},
+		"classname": {
+			{`(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*`, NameClass, Pop(1)},
+		},
+		"functionname": {
+			Include("magicfuncs"),
+			{`(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*`, NameFunction, Pop(1)},
+			Default(Pop(1)),
+		},
+		"string": {
+			{`"`, LiteralStringDouble, Pop(1)},
+			{`[^{$"\\]+`, LiteralStringDouble, nil},
+			{`\\([nrt"$\\]|[0-7]{1,3}|x[0-9a-f]{1,2})`, LiteralStringEscape, nil},
+			{`\$(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*(\[\S+?\]|->(?:[\\_a-z]|[^\x00-\x7f])(?:[\\\w]|[^\x00-\x7f])*)?`, LiteralStringInterpol, nil},
+			{`(\{\$\{)(.*?)(\}\})`, ByGroups(LiteralStringInterpol, UsingSelf("root"), LiteralStringInterpol), nil},
+			{`(\{)(\$.*?)(\})`, ByGroups(LiteralStringInterpol, UsingSelf("root"), LiteralStringInterpol), nil},
+			{`(\$\{)(\S+)(\})`, ByGroups(LiteralStringInterpol, NameVariable, LiteralStringInterpol), nil},
+			{`[${\\]`, LiteralStringDouble, nil},
+		},
+	},
+).SetAnalyser(func(text string) float32 {
+	if strings.Contains(text, "<?php") {
+		return 0.5
+	}
+	return 0.0
+})))