Pagination, readable error messages to user, syntax highlighting started.

Pagination now works. Temporary hardcoded 10 pastes per page, will be put
in configuration later. Maybe.

From now user will receive readable error message if error occured.

Started to work on syntax highlighting, tried to make lexers detection
work but apparently to no avail.

vendor/github.com/alecthomas/chroma/lexers/d/dart.go

@@ -0,0 +1,91 @@
+package d
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Dart lexer.
+var Dart = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "Dart",
+		Aliases:   []string{"dart"},
+		Filenames: []string{"*.dart"},
+		MimeTypes: []string{"text/x-dart"},
+		DotAll:    true,
+	},
+	Rules{
+		"root": {
+			Include("string_literal"),
+			{`#!(.*?)$`, CommentPreproc, nil},
+			{`\b(import|export)\b`, Keyword, Push("import_decl")},
+			{`\b(library|source|part of|part)\b`, Keyword, nil},
+			{`[^\S\n]+`, Text, nil},
+			{`//.*?\n`, CommentSingle, nil},
+			{`/\*.*?\*/`, CommentMultiline, nil},
+			{`\b(class)\b(\s+)`, ByGroups(KeywordDeclaration, Text), Push("class")},
+			{`\b(assert|break|case|catch|continue|default|do|else|finally|for|if|in|is|new|return|super|switch|this|throw|try|while)\b`, Keyword, nil},
+			{`\b(abstract|async|await|const|extends|factory|final|get|implements|native|operator|set|static|sync|typedef|var|with|yield)\b`, KeywordDeclaration, nil},
+			{`\b(bool|double|dynamic|int|num|Object|String|void)\b`, KeywordType, nil},
+			{`\b(false|null|true)\b`, KeywordConstant, nil},
+			{`[~!%^&*+=|?:<>/-]|as\b`, Operator, nil},
+			{`[a-zA-Z_$]\w*:`, NameLabel, nil},
+			{`[a-zA-Z_$]\w*`, Name, nil},
+			{`[(){}\[\],.;]`, Punctuation, nil},
+			{`0[xX][0-9a-fA-F]+`, LiteralNumberHex, nil},
+			{`\d+(\.\d*)?([eE][+-]?\d+)?`, LiteralNumber, nil},
+			{`\.\d+([eE][+-]?\d+)?`, LiteralNumber, nil},
+			{`\n`, Text, nil},
+		},
+		"class": {
+			{`[a-zA-Z_$]\w*`, NameClass, Pop(1)},
+		},
+		"import_decl": {
+			Include("string_literal"),
+			{`\s+`, Text, nil},
+			{`\b(as|show|hide)\b`, Keyword, nil},
+			{`[a-zA-Z_$]\w*`, Name, nil},
+			{`\,`, Punctuation, nil},
+			{`\;`, Punctuation, Pop(1)},
+		},
+		"string_literal": {
+			{`r"""([\w\W]*?)"""`, LiteralStringDouble, nil},
+			{`r'''([\w\W]*?)'''`, LiteralStringSingle, nil},
+			{`r"(.*?)"`, LiteralStringDouble, nil},
+			{`r'(.*?)'`, LiteralStringSingle, nil},
+			{`"""`, LiteralStringDouble, Push("string_double_multiline")},
+			{`'''`, LiteralStringSingle, Push("string_single_multiline")},
+			{`"`, LiteralStringDouble, Push("string_double")},
+			{`'`, LiteralStringSingle, Push("string_single")},
+		},
+		"string_common": {
+			{`\\(x[0-9A-Fa-f]{2}|u[0-9A-Fa-f]{4}|u\{[0-9A-Fa-f]*\}|[a-z'\"$\\])`, LiteralStringEscape, nil},
+			{`(\$)([a-zA-Z_]\w*)`, ByGroups(LiteralStringInterpol, Name), nil},
+			{`(\$\{)(.*?)(\})`, ByGroups(LiteralStringInterpol, UsingSelf("root"), LiteralStringInterpol), nil},
+		},
+		"string_double": {
+			{`"`, LiteralStringDouble, Pop(1)},
+			{`[^"$\\\n]+`, LiteralStringDouble, nil},
+			Include("string_common"),
+			{`\$+`, LiteralStringDouble, nil},
+		},
+		"string_double_multiline": {
+			{`"""`, LiteralStringDouble, Pop(1)},
+			{`[^"$\\]+`, LiteralStringDouble, nil},
+			Include("string_common"),
+			{`(\$|\")+`, LiteralStringDouble, nil},
+		},
+		"string_single": {
+			{`'`, LiteralStringSingle, Pop(1)},
+			{`[^'$\\\n]+`, LiteralStringSingle, nil},
+			Include("string_common"),
+			{`\$+`, LiteralStringSingle, nil},
+		},
+		"string_single_multiline": {
+			{`'''`, LiteralStringSingle, Pop(1)},
+			{`[^\'$\\]+`, LiteralStringSingle, nil},
+			Include("string_common"),
+			{`(\$|\')+`, LiteralStringSingle, nil},
+		},
+	},
+))

vendor/github.com/alecthomas/chroma/lexers/d/diff.go

@@ -0,0 +1,29 @@
+package d
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Diff lexer.
+var Diff = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "Diff",
+		Aliases:   []string{"diff", "udiff"},
+		EnsureNL:  true,
+		Filenames: []string{"*.diff", "*.patch"},
+		MimeTypes: []string{"text/x-diff", "text/x-patch"},
+	},
+	Rules{
+		"root": {
+			{` .*\n`, Text, nil},
+			{`\+.*\n`, GenericInserted, nil},
+			{`-.*\n`, GenericDeleted, nil},
+			{`!.*\n`, GenericStrong, nil},
+			{`@.*\n`, GenericSubheading, nil},
+			{`([Ii]ndex|diff).*\n`, GenericHeading, nil},
+			{`=.*\n`, GenericHeading, nil},
+			{`.*\n`, Text, nil},
+		},
+	},
+))

vendor/github.com/alecthomas/chroma/lexers/d/django.go

@@ -0,0 +1,53 @@
+package d
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Django/Jinja lexer.
+var DjangoJinja = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "Django/Jinja",
+		Aliases:   []string{"django", "jinja"},
+		Filenames: []string{},
+		MimeTypes: []string{"application/x-django-templating", "application/x-jinja"},
+		DotAll:    true,
+	},
+	Rules{
+		"root": {
+			{`[^{]+`, Other, nil},
+			{`\{\{`, CommentPreproc, Push("var")},
+			{`\{[*#].*?[*#]\}`, Comment, nil},
+			{`(\{%)(-?\s*)(comment)(\s*-?)(%\})(.*?)(\{%)(-?\s*)(endcomment)(\s*-?)(%\})`, ByGroups(CommentPreproc, Text, Keyword, Text, CommentPreproc, Comment, CommentPreproc, Text, Keyword, Text, CommentPreproc), nil},
+			{`(\{%)(-?\s*)(raw)(\s*-?)(%\})(.*?)(\{%)(-?\s*)(endraw)(\s*-?)(%\})`, ByGroups(CommentPreproc, Text, Keyword, Text, CommentPreproc, Text, CommentPreproc, Text, Keyword, Text, CommentPreproc), nil},
+			{`(\{%)(-?\s*)(filter)(\s+)([a-zA-Z_]\w*)`, ByGroups(CommentPreproc, Text, Keyword, Text, NameFunction), Push("block")},
+			{`(\{%)(-?\s*)([a-zA-Z_]\w*)`, ByGroups(CommentPreproc, Text, Keyword), Push("block")},
+			{`\{`, Other, nil},
+		},
+		"varnames": {
+			{`(\|)(\s*)([a-zA-Z_]\w*)`, ByGroups(Operator, Text, NameFunction), nil},
+			{`(is)(\s+)(not)?(\s+)?([a-zA-Z_]\w*)`, ByGroups(Keyword, Text, Keyword, Text, NameFunction), nil},
+			{`(_|true|false|none|True|False|None)\b`, KeywordPseudo, nil},
+			{`(in|as|reversed|recursive|not|and|or|is|if|else|import|with(?:(?:out)?\s*context)?|scoped|ignore\s+missing)\b`, Keyword, nil},
+			{`(loop|block|super|forloop)\b`, NameBuiltin, nil},
+			{`[a-zA-Z_][\w-]*`, NameVariable, nil},
+			{`\.\w+`, NameVariable, nil},
+			{`:?"(\\\\|\\"|[^"])*"`, LiteralStringDouble, nil},
+			{`:?'(\\\\|\\'|[^'])*'`, LiteralStringSingle, nil},
+			{`([{}()\[\]+\-*/,:~]|[><=]=?)`, Operator, nil},
+			{`[0-9](\.[0-9]*)?(eE[+-][0-9])?[flFLdD]?|0[xX][0-9a-fA-F]+[Ll]?`, LiteralNumber, nil},
+		},
+		"var": {
+			{`\s+`, Text, nil},
+			{`(-?)(\}\})`, ByGroups(Text, CommentPreproc), Pop(1)},
+			Include("varnames"),
+		},
+		"block": {
+			{`\s+`, Text, nil},
+			{`(-?)(%\})`, ByGroups(Text, CommentPreproc), Pop(1)},
+			Include("varnames"),
+			{`.`, Punctuation, nil},
+		},
+	},
+))

vendor/github.com/alecthomas/chroma/lexers/d/docker.go

@@ -0,0 +1,27 @@
+package d
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	. "github.com/alecthomas/chroma/lexers/b"
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Docker lexer.
+var Docker = internal.Register(MustNewLexer(
+	&Config{
+		Name:            "Docker",
+		Aliases:         []string{"docker", "dockerfile"},
+		Filenames:       []string{"Dockerfile", "*.docker"},
+		MimeTypes:       []string{"text/x-dockerfile-config"},
+		CaseInsensitive: true,
+	},
+	Rules{
+		"root": {
+			{`^(ONBUILD)(\s+)((?:FROM|MAINTAINER|CMD|EXPOSE|ENV|ADD|ENTRYPOINT|VOLUME|WORKDIR))\b`, ByGroups(NameKeyword, TextWhitespace, Keyword), nil},
+			{`^((?:FROM|MAINTAINER|CMD|EXPOSE|ENV|ADD|ENTRYPOINT|VOLUME|WORKDIR))\b(.*)`, ByGroups(Keyword, LiteralString), nil},
+			{`#.*`, Comment, nil},
+			{`RUN`, Keyword, nil},
+			{`(.*\\\n)*.+`, Using(Bash), nil},
+		},
+	},
+))

vendor/github.com/alecthomas/chroma/lexers/d/dtd.go

@@ -0,0 +1,69 @@
+package d
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Dtd lexer.
+var Dtd = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "DTD",
+		Aliases:   []string{"dtd"},
+		Filenames: []string{"*.dtd"},
+		MimeTypes: []string{"application/xml-dtd"},
+		DotAll:    true,
+	},
+	Rules{
+		"root": {
+			Include("common"),
+			{`(<!ELEMENT)(\s+)(\S+)`, ByGroups(Keyword, Text, NameTag), Push("element")},
+			{`(<!ATTLIST)(\s+)(\S+)`, ByGroups(Keyword, Text, NameTag), Push("attlist")},
+			{`(<!ENTITY)(\s+)(\S+)`, ByGroups(Keyword, Text, NameEntity), Push("entity")},
+			{`(<!NOTATION)(\s+)(\S+)`, ByGroups(Keyword, Text, NameTag), Push("notation")},
+			{`(<!\[)([^\[\s]+)(\s*)(\[)`, ByGroups(Keyword, NameEntity, Text, Keyword), nil},
+			{`(<!DOCTYPE)(\s+)([^>\s]+)`, ByGroups(Keyword, Text, NameTag), nil},
+			{`PUBLIC|SYSTEM`, KeywordConstant, nil},
+			{`[\[\]>]`, Keyword, nil},
+		},
+		"common": {
+			{`\s+`, Text, nil},
+			{`(%|&)[^;]*;`, NameEntity, nil},
+			{`<!--`, Comment, Push("comment")},
+			{`[(|)*,?+]`, Operator, nil},
+			{`"[^"]*"`, LiteralStringDouble, nil},
+			{`\'[^\']*\'`, LiteralStringSingle, nil},
+		},
+		"comment": {
+			{`[^-]+`, Comment, nil},
+			{`-->`, Comment, Pop(1)},
+			{`-`, Comment, nil},
+		},
+		"element": {
+			Include("common"),
+			{`EMPTY|ANY|#PCDATA`, KeywordConstant, nil},
+			{`[^>\s|()?+*,]+`, NameTag, nil},
+			{`>`, Keyword, Pop(1)},
+		},
+		"attlist": {
+			Include("common"),
+			{`CDATA|IDREFS|IDREF|ID|NMTOKENS|NMTOKEN|ENTITIES|ENTITY|NOTATION`, KeywordConstant, nil},
+			{`#REQUIRED|#IMPLIED|#FIXED`, KeywordConstant, nil},
+			{`xml:space|xml:lang`, KeywordReserved, nil},
+			{`[^>\s|()?+*,]+`, NameAttribute, nil},
+			{`>`, Keyword, Pop(1)},
+		},
+		"entity": {
+			Include("common"),
+			{`SYSTEM|PUBLIC|NDATA`, KeywordConstant, nil},
+			{`[^>\s|()?+*,]+`, NameEntity, nil},
+			{`>`, Keyword, Pop(1)},
+		},
+		"notation": {
+			Include("common"),
+			{`SYSTEM|PUBLIC`, KeywordConstant, nil},
+			{`[^>\s|()?+*,]+`, NameAttribute, nil},
+			{`>`, Keyword, Pop(1)},
+		},
+	},
+))