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>

1 files changed, 380 insertions, 0 deletions

diff --git a/web_src/less/_chroma.less b/web_src/less/_chroma.less
new file mode 100644
index 0000000000..2940f17f3b
--- /dev/null
+++ b/web_src/less/_chroma.less
@@ -0,0 +1,380 @@
+/* Background */
+
+.chroma {
+    background-color: #ffffff;
+}
+/* LineTableTD */
+
+.chroma .lntd {
+    vertical-align: top;
+    padding: 0;
+    margin: 0;
+    border: 0;
+}
+/* LineTable */
+
+.chroma .lntable {
+    border-spacing: 0;
+    padding: 0;
+    margin: 0;
+    border: 0;
+    width: auto;
+    overflow: auto;
+    display: block;
+}
+/* LineHighlight */
+
+.chroma .hl {
+    display: block;
+    width: 100%;
+    background-color: #e5e5e5;
+}
+/* LineNumbersTable */
+
+.chroma .lnt {
+    margin-right: .4em;
+    padding: 0 .4em;
+    color: #7f7f7f;
+}
+/* LineNumbers */
+
+.chroma .ln {
+    margin-right: .4em;
+    padding: 0 .4em;
+    color: #7f7f7f;
+}
+/* Keyword */
+
+.chroma .k {
+    color: #d73a49;
+}
+/* KeywordConstant */
+
+.chroma .kc {
+    color: #d73a49;
+}
+/* KeywordDeclaration */
+
+.chroma .kd {
+    color: #d73a49;
+}
+/* KeywordNamespace */
+
+.chroma .kn {
+    color: #d73a49;
+}
+/* KeywordPseudo */
+
+.chroma .kp {
+    color: #d73a49;
+}
+/* KeywordReserved */
+
+.chroma .kr {
+    color: #d73a49;
+}
+/* KeywordType */
+
+.chroma .kt {
+    color: #445588;
+}
+/* NameAttribute */
+
+.chroma .na {
+    color: #d73a49;
+}
+/* NameBuiltin */
+
+.chroma .nb {
+    color: #005cc5;
+}
+/* NameBuiltinPseudo */
+
+.chroma .bp {
+    color: #999999;
+}
+/* NameClass */
+
+.chroma .nc {
+    color: #445588;
+}
+/* NameConstant */
+
+.chroma .no {
+    color: #008080;
+}
+/* NameDecorator */
+
+.chroma .nd {
+    color: #3c5d5d;
+}
+/* NameEntity */
+
+.chroma .ni {
+    color: #6f42c1;
+}
+/* NameException */
+
+.chroma .ne {
+    color: #990000;
+}
+/* NameFunction */
+
+.chroma .nf {
+    color: #005cc5;
+}
+/* NameLabel */
+
+.chroma .nl {
+    color: #990000;
+}
+/* NameNamespace */
+
+.chroma .nn {
+    color: #555555;
+}
+/* NameOther */
+
+.chroma .nx {
+    color: #24292e;
+}
+/* NameTag */
+
+.chroma .nt {
+    color: #22863a;
+}
+/* NameVariable */
+
+.chroma .nv {
+    color: #008080;
+}
+/* NameVariableClass */
+
+.chroma .vc {
+    color: #008080;
+}
+/* NameVariableGlobal */
+
+.chroma .vg {
+    color: #008080;
+}
+/* NameVariableInstance */
+
+.chroma .vi {
+    color: #008080;
+}
+/* LiteralString */
+
+.chroma .s {
+    color: #032f62;
+}
+/* LiteralStringAffix */
+
+.chroma .sa {
+    color: #032f62;
+}
+/* LiteralStringBacktick */
+
+.chroma .sb {
+    color: #032f62;
+}
+/* LiteralStringChar */
+
+.chroma .sc {
+    color: #032f62;
+}
+/* LiteralStringDelimiter */
+
+.chroma .dl {
+    color: #032f62;
+}
+/* LiteralStringDoc */
+
+.chroma .sd {
+    color: #032f62;
+}
+/* LiteralStringDouble */
+
+.chroma .s2 {
+    color: #032f62;
+}
+/* LiteralStringEscape */
+
+.chroma .se {
+    color: #032f62;
+}
+/* LiteralStringHeredoc */
+
+.chroma .sh {
+    color: #032f62;
+}
+/* LiteralStringInterpol */
+
+.chroma .si {
+    color: #032f62;
+}
+/* LiteralStringOther */
+
+.chroma .sx {
+    color: #032f62;
+}
+/* LiteralStringRegex */
+
+.chroma .sr {
+    font-weight: bold;
+    color: #22863a;
+}
+/* LiteralStringSingle */
+
+.chroma .s1 {
+    color: #24292e;
+}
+/* LiteralStringSymbol */
+
+.chroma .ss {
+    color: #032f62;
+}
+/* LiteralNumber */
+
+.chroma .m {
+    color: #009999;
+}
+/* LiteralNumberBin */
+
+.chroma .mb {
+    color: #009999;
+}
+/* LiteralNumberFloat */
+
+.chroma .mf {
+    color: #009999;
+}
+/* LiteralNumberHex */
+
+.chroma .mh {
+    color: #009999;
+}
+/* LiteralNumberInteger */
+
+.chroma .mi {
+    color: #009999;
+}
+/* LiteralNumberIntegerLong */
+
+.chroma .il {
+    color: #009999;
+}
+/* LiteralNumberOct */
+
+.chroma .mo {
+    color: #009999;
+}
+/* Operator */
+
+.chroma .o {
+    color: #d73a49;
+}
+/* OperatorWord */
+
+.chroma .ow {
+    color: #d73a49;
+}
+/* Comment */
+
+.chroma .c {
+    color: #6a737d;
+}
+/* CommentHashbang */
+
+.chroma .ch {
+    color: #6a737d;
+}
+/* CommentMultiline */
+
+.chroma .cm {
+    color: #999988;
+}
+/* CommentSingle */
+
+.chroma .c1 {
+    color: #6a737d;
+}
+/* CommentSpecial */
+
+.chroma .cs {
+    color: #999999;
+    font-style: italic;
+}
+/* CommentPreproc */
+
+.chroma .cp {
+    color: #999999;
+}
+/* CommentPreprocFile */
+
+.chroma .cpf {
+    color: #999999;
+}
+/* GenericDeleted */
+
+.chroma .gd {
+    color: #000000;
+    background-color: #ffdddd;
+}
+/* GenericEmph */
+
+.chroma .ge {
+    color: #000000;
+    font-style: italic;
+}
+/* GenericError */
+
+.chroma .gr {
+    color: #aa0000;
+}
+/* GenericHeading */
+
+.chroma .gh {
+    color: #999999;
+}
+/* GenericInserted */
+
+.chroma .gi {
+    color: #000000;
+    background-color: #ddffdd;
+}
+/* GenericOutput */
+
+.chroma .go {
+    color: #888888;
+}
+/* GenericPrompt */
+
+.chroma .gp {
+    color: #555555;
+}
+/* GenericStrong */
+
+.chroma .gs {
+    font-weight: bold;
+}
+/* GenericSubheading */
+
+.chroma .gu {
+    color: #aaaaaa;
+}
+/* GenericTraceback */
+
+.chroma .gt {
+    color: #aa0000;
+}
+/* GenericUnderline */
+
+.chroma .gl {
+    text-decoration: underline;
+}
+/* TextWhitespace */
+
+.chroma .w {
+    color: #bbbbbb;
+}