Automatically detect indentation, closes #529v4.8.0

4 files changed, 420 insertions, 1 deletions

diff --git a/README.md b/README.md
index 7424431c..f53acd5f 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ A collection of language packs for Vim.
 - It is more secure because scripts loaded for all extensions are generated by vim-polyglot (ftdetect).
 - Solid syntax and indentation support (other features skipped). Only the best language packs.
 - All unnecessary files are ignored (like enormous documentation from php support).
-- No support for esoteric languages, only most popular ones (modern too, like `slim`).
+- Automatically detect indentation (includes performance-optimized version of [vim-sleuth](https://github.com/tpope/vim-sleuth))
 - Each build is tested by automated vimrunner script on CI. See `spec` directory.
 
 \*To be completely honest, optimized `ftdetect` script takes around `19ms` to load.
diff --git a/autoload/sleuth.vim b/autoload/sleuth.vim
new file mode 100644
index 00000000..1c9fbefb
--- /dev/null
+++ b/autoload/sleuth.vim
@@ -0,0 +1,221 @@
+let s:globs = {
+  \ '8th': '{*.8th,}',
+  \ 'Dockerfile': '{*.dockerfile,*.dock,*.Dockerfile,Dockerfile,dockerfile,Dockerfile*,}',
+  \ 'Jenkinsfile': '{*.jenkinsfile,*.Jenkinsfile,Jenkinsfile,Jenkinsfile*,}',
+  \ 'a2ps': '{a2psrc,.a2psrc,}',
+  \ 'a65': '{*.a65,}',
+  \ 'aap': '{*.aap,}',
+  \ 'abap': '{*.abap,}',
+  \ 'abaqus': '{*.inp,}',
+  \ 'abc': '{*.abc,}',
+  \ 'abel': '{*.abl,}',
+  \ 'acedb': '{*.wrm,}',
+  \ 'ada': '{*.adb,*.ads,*.ada,*.gpr,}',
+  \ 'ahdl': '{*.tdf,}',
+  \ 'aidl': '{*.aidl,}',
+  \ 'alsaconf': '{.asoundrc,}',
+  \ 'aml': '{*.aml,}',
+  \ 'ampl': '{*.run,}',
+  \ 'ant': '{build.xml,}',
+  \ 'apache': '{.htaccess,}',
+  \ 'apiblueprint': '{*.apib,}',
+  \ 'applescript': '{*.applescript,*.scpt,}',
+  \ 'aptconf': '{apt.conf,}',
+  \ 'arch': '{.arch-inventory,=tagging-method,}',
+  \ 'arduino': '{*.pde,*.ino,}',
+  \ 'art': '{*.art,}',
+  \ 'asciidoc': '{*.asciidoc,*.adoc,*.asc,}',
+  \ 'asl': '{*.asl,*.dsl,}',
+  \ 'asn': '{*.asn,*.asn1,}',
+  \ 'aspperl': '{*.asp,}',
+  \ 'aspvbs': '{*.asa,*.asp,}',
+  \ 'atlas': '{*.atl,*.as,}',
+  \ 'autohotkey': '{*.ahk,*.ahkl,}',
+  \ 'autoit': '{*.au3,}',
+  \ 'automake': '{[Mm]akefile.am,GNUmakefile.am,}',
+  \ 'ave': '{*.ave,}',
+  \ 'awk': '{*.awk,}',
+  \ 'blade': '{*.blade,*.blade.php,}',
+  \ 'brewfile': '{Brewfile,}',
+  \ 'c': '{*.c,*.cats,*.h,*.idc,}',
+  \ 'caddyfile': '{Caddyfile,}',
+  \ 'carp': '{*.carp,}',
+  \ 'clojure': '{*.clj,*.boot,*.cl2,*.cljc,*.cljs,*.cljs.hl,*.cljscm,*.cljx,*.hic,*.edn,riemann.config,build.boot,profile.boot,}',
+  \ 'cmake': '{*.cmake,*.cmake.in,CMakeLists.txt,}',
+  \ 'coffee': '{*.coffee,*._coffee,*.cake,*.cjsx,*.iced,*.coffeekup,Cakefile,}',
+  \ 'cpp': '{*.cpp,*.c++,*.cc,*.cp,*.cxx,*.h,*.h++,*.hh,*.hpp,*.hxx,*.inc,*.inl,*.ino,*.ipp,*.re,*.tcc,*.tpp,}',
+  \ 'cql': '{*.cql,}',
+  \ 'cryptol': '{*.cry,*.cyl,*.lcry,*.lcyl,}',
+  \ 'crystal': '{*.cr,Projectfile,}',
+  \ 'csv': '{*.csv,*.tsv,*.tab,}',
+  \ 'cucumber': '{*.feature,*.story,}',
+  \ 'cuesheet': '{*.cue,}',
+  \ 'd': '{*.d,*.di,}',
+  \ 'dart': '{*.dart,}',
+  \ 'dcov': '{*.lst,}',
+  \ 'dd': '{*.dd,}',
+  \ 'ddoc': '{*.ddoc,}',
+  \ 'dhall': '{*.dhall,}',
+  \ 'dosini': '{*.wrap,}',
+  \ 'dsdl': '{*.sdl,}',
+  \ 'dune': '{jbuild,dune,dune-project,dune-workspace,}',
+  \ 'ecrystal': '{*.ecr,}',
+  \ 'eelixir': '{*.eex,*.leex,}',
+  \ 'elf': '{*.am,}',
+  \ 'elixir': '{*.ex,*.exs,mix.lock,}',
+  \ 'elm': '{*.elm,}',
+  \ 'embeddedpuppet': '{*.epp,}',
+  \ 'ember-script': '{*.em,*.emberscript,}',
+  \ 'emblem': '{*.emblem,*.em,}',
+  \ 'erlang': '{*.erl,*.app.src,*.es,*.escript,*.hrl,*.xrl,*.yrl,*.app,*.yaws,Emakefile,rebar.config,rebar.config.lock,rebar.lock,}',
+  \ 'eruby': '{*.erb,*.erb.deface,*.rhtml,}',
+  \ 'fbs': '{*.fbs,}',
+  \ 'fennel': '{*.fnl,}',
+  \ 'ferm': '{*.ferm,ferm.conf,}',
+  \ 'fish': '{*.fish,}',
+  \ 'flow': '{*.flow,}',
+  \ 'forth': '{*.fs,*.ft,*.fth,}',
+  \ 'fsharp': '{*.fs,*.fsi,*.fsx,}',
+  \ 'gdscript3': '{*.gd,}',
+  \ 'gitcommit': '{,}',
+  \ 'gitconfig': '{*.gitconfig,.gitconfig,.gitmodules,}',
+  \ 'gitrebase': '{git-rebase-todo,}',
+  \ 'gitsendemail': '{.gitsendemail.*,}',
+  \ 'glsl': '{*.glsl,*.fp,*.frag,*.frg,*.fs,*.fsh,*.fshader,*.geo,*.geom,*.glslf,*.glslv,*.gs,*.gshader,*.shader,*.tesc,*.tese,*.vert,*.vrx,*.vsh,*.vshader,*.comp,}',
+  \ 'gmpl': '{*.mod,}',
+  \ 'gnuplot': '{*.gp,*.gnu,*.gnuplot,*.p,*.plot,*.plt,}',
+  \ 'go': '{*.go,}',
+  \ 'gohtmltmpl': '{*.tmpl,}',
+  \ 'gomod': '{go.mod,}',
+  \ 'graphql': '{*.graphql,*.gql,*.graphqls,}',
+  \ 'groovy': '{*.gradle,}',
+  \ 'grub': '{,}',
+  \ 'haml': '{*.haml,*.haml.deface,*.hamlc,*.hamlbars,}',
+  \ 'haproxy': '{*.cfg,haproxy.cfg,haproxy*.c*,}',
+  \ 'haskell': '{*.hs,*.hs-boot,*.hsc,*.bpk,*.hsig,}',
+  \ 'haxe': '{*.hx,*.hxsl,}',
+  \ 'hcl': '{*.hcl,*.nomad,*.tf,*.tfvars,*.workflow,Appfile,}',
+  \ 'helm': '{,}',
+  \ 'help': '{,}',
+  \ 'hive': '{*.q,*.hql,*.ql,}',
+  \ 'html': '{*.html,*.htm,*.html.hl,*.inc,*.st,*.xht,*.xhtml,}',
+  \ 'html.twig': '{*.twig,}',
+  \ 'i3config': '{*.i3.config,*.i3config,i3.config,i3config,.i3.config,.i3config,}',
+  \ 'icalendar': '{*.ics,}',
+  \ 'idris': '{*.idr,*.lidr,idris-response,}',
+  \ 'ion': '{*.ion,}',
+  \ 'javascript': '{*.js,*._js,*.bones,*.cjs,*.es,*.es6,*.frag,*.gs,*.jake,*.jsb,*.jscad,*.jsfl,*.jsm,*.jss,*.mjs,*.njs,*.pac,*.sjs,*.ssjs,*.xsjs,*.xsjslib,Jakefile,}',
+  \ 'javascriptreact': '{*.jsx,}',
+  \ 'jinja.html': '{*.jinja,*.j2,*.jinja2,*.njk,}',
+  \ 'jq': '{*.jq,.jqrc,}',
+  \ 'json': '{*.json,*.avsc,*.geojson,*.gltf,*.har,*.ice,*.JSON-tmLanguage,*.jsonl,*.mcmeta,*.tfstate,*.tfstate.backup,*.topojson,*.webapp,*.webmanifest,*.yy,*.yyp,*.jsonp,*.template,.arcconfig,.htmlhintrc,.tern-config,.tern-project,.watchmanconfig,composer.lock,mcmod.info,}',
+  \ 'json5': '{*.json5,}',
+  \ 'jsonnet': '{*.jsonnet,*.libsonnet,}',
+  \ 'jst': '{*.ejs,*.ect,*.jst,}',
+  \ 'julia': '{*.jl,}',
+  \ 'kotlin': '{*.kt,*.ktm,*.kts,}',
+  \ 'ledger': '{*.ldg,*.ledger,*.journal,}',
+  \ 'less': '{*.less,}',
+  \ 'lilypond': '{*.ly,*.ily,}',
+  \ 'litcoffee': '{*.litcoffee,*.coffee.md,}',
+  \ 'livescript': '{*.ls,*._ls,Slakefile,}',
+  \ 'llvm': '{*.ll,}',
+  \ 'log': '{*.log,*.LOG,*_log,*_LOG,}',
+  \ 'lua': '{*.lua,*.fcgi,*.nse,*.p8,*.pd_lua,*.rbxs,*.rockspec,*.wlua,.luacheckrc,}',
+  \ 'm4': '{*.m4,*.at,}',
+  \ 'mako': '{*.mako,*.mao,}',
+  \ 'markdown': '{*.md,*.markdown,*.mdown,*.mdwn,*.mdx,*.mkd,*.mkdn,*.mkdown,*.ronn,*.workbook,contents.lr,}',
+  \ 'markdown.mdx': '{*.mdx,}',
+  \ 'meson': '{meson.build,meson_options.txt,}',
+  \ 'mma': '{*.mathematica,*.cdf,*.m,*.ma,*.mt,*.nb,*.nbp,*.wl,*.wlt,*.wls,}',
+  \ 'moon': '{*.moon,}',
+  \ 'murphi': '{*.m,}',
+  \ 'mustache': '{*.handlebars,*.hbs,*.hulk,*.hjs,*.mustache,*.njk,*.hogan,*.hdbs,*.hb,}',
+  \ 'nginx': '{*.nginx,*.nginxconf,*.vhost,nginx.conf,nginx*.conf,*nginx.conf,}',
+  \ 'nim': '{*.nim,*.nim.cfg,*.nimble,*.nimrod,*.nims,nim.cfg,}',
+  \ 'nix': '{*.nix,}',
+  \ 'oasis': '{_oasis,}',
+  \ 'objc': '{*.m,*.h,}',
+  \ 'ocaml': '{*.ml,*.eliom,*.eliomi,*.ml4,*.mli,*.mll,*.mly,*.mlt,*.mlp,*.mlip,*.mli.cppo,*.ml.cppo,.ocamlinit,}',
+  \ 'ocamlbuild_tags': '{_tags,}',
+  \ 'ocpbuild': '{*.ocp,}',
+  \ 'ocpbuildroot': '{*.root,}',
+  \ 'octave': '{*.oct,*.m,}',
+  \ 'omake': '{*.om,OMakefile,OMakeroot,OMakeroot.in,}',
+  \ 'opam': '{*.opam,*.opam.template,opam,}',
+  \ 'opencl': '{*.cl,*.opencl,}',
+  \ 'perl': '{*.pl,*.al,*.cgi,*.fcgi,*.perl,*.ph,*.plx,*.pm,*.psgi,*.t,Makefile.PL,Rexfile,ack,cpanfile,}',
+  \ 'php': '{*.php,*.aw,*.ctp,*.fcgi,*.inc,*.php3,*.php4,*.php5,*.phps,*.phpt,.php,.php_cs,.php_cs.dist,Phakefile,}',
+  \ 'plantuml': '{*.puml,*.iuml,*.plantuml,*.uml,*.pu,}',
+  \ 'pony': '{*.pony,}',
+  \ 'proto': '{*.proto,}',
+  \ 'ps1': '{*.ps1,*.psd1,*.psm1,*.pssc,}',
+  \ 'ps1xml': '{*.ps1xml,}',
+  \ 'pug': '{*.jade,*.pug,}',
+  \ 'puppet': '{*.pp,Modulefile,}',
+  \ 'purescript': '{*.purs,}',
+  \ 'python': '{*.py,*.cgi,*.fcgi,*.gyp,*.gypi,*.lmi,*.py3,*.pyde,*.pyi,*.pyp,*.pyt,*.pyw,*.rpy,*.smk,*.spec,*.tac,*.wsgi,*.xpy,.gclient,DEPS,SConscript,SConstruct,Snakefile,wscript,}',
+  \ 'qmake': '{*.pro,*.pri,}',
+  \ 'qml': '{*.qml,*.qbs,}',
+  \ 'r': '{*.r,*.rd,*.rsx,*.s,*.S,.Rprofile,expr-dist,}',
+  \ 'racket': '{*.rkt,*.rktd,*.rktl,*.scrbl,}',
+  \ 'ragel': '{*.rl,}',
+  \ 'raku': '{*.6pl,*.6pm,*.nqp,*.p6,*.p6l,*.p6m,*.pl,*.pl6,*.pm,*.pm6,*.t,*.rakudoc,*.rakutest,*.raku,*.rakumod,*.pod6,*.t6,}',
+  \ 'raml': '{*.raml,}',
+  \ 'razor': '{*.cshtml,*.razor,}',
+  \ 'reason': '{*.re,*.rei,}',
+  \ 'requirements': '{*.pip,*requirements.{txt,in},*require.{txt,in},constraints.{txt,in},}',
+  \ 'rhelp': '{*.rd,}',
+  \ 'rst': '{*.rst,*.rest,*.rest.txt,*.rst.txt,}',
+  \ 'ruby': '{*.rb,*.builder,*.eye,*.fcgi,*.gemspec,*.god,*.jbuilder,*.mspec,*.pluginspec,*.podspec,*.rabl,*.rake,*.rbi,*.rbuild,*.rbw,*.rbx,*.ru,*.ruby,*.spec,*.thor,*.watchr,*.rxml,*.rjs,*.rant,*.axlsx,*.cap,*.opal,.irbrc,.pryrc,.simplecov,Appraisals,Berksfile,Brewfile,Buildfile,Capfile,Dangerfile,Deliverfile,Fastfile,Gemfile,Gemfile.lock,Guardfile,Jarfile,Mavenfile,Podfile,Puppetfile,Rakefile,Snapfile,Thorfile,Vagrantfile,buildfile,Rantfile,.autotest,Cheffile,KitchenSink,Routefile,.Guardfile,.Brewfile,vagrantfile,[Rr]akefile*,*_spec.rb,}',
+  \ 'rust': '{*.rs,*.rs.in,}',
+  \ 'sbt.scala': '{*.sbt,}',
+  \ 'scala': '{*.scala,*.kojo,*.sbt,*.sc,}',
+  \ 'scss': '{*.scss,}',
+  \ 'sexplib': '{*.sexp,}',
+  \ 'sh': '{*.sh,*.bash,*.bats,*.cgi,*.command,*.env,*.fcgi,*.ksh,*.sh.in,*.tmux,*.tool,*.zsh,.bash_aliases,.bash_history,.bash_logout,.bash_profile,.bashrc,.cshrc,.env,.env.example,.flaskenv,.login,.profile,.zlogin,.zlogout,.zprofile,.zshenv,.zshrc,9fs,PKGBUILD,bash_aliases,bash_logout,bash_profile,bashrc,cshrc,gradlew,login,man,profile,zlogin,zlogout,zprofile,zshenv,zshrc,}',
+  \ 'slim': '{*.slim,}',
+  \ 'slime': '{*.slime,}',
+  \ 'smt2': '{*.smt2,*.smt,}',
+  \ 'solidity': '{*.sol,}',
+  \ 'sql': '{*.pgsql,*.sql,}',
+  \ 'stylus': '{*.styl,*.stylus,}',
+  \ 'svelte': '{*.svelte,}',
+  \ 'svg': '{*.svg,}',
+  \ 'swift': '{*.swift,}',
+  \ 'sxhkdrc': '{*.sxhkdrc,sxhkdrc,}',
+  \ 'systemd': '{*.automount,*.mount,*.path,*.service,*.socket,*.swap,*.target,*.timer,}',
+  \ 'tablegen': '{*.td,}',
+  \ 'terraform': '{*.hcl,*.nomad,*.tf,*.tfvars,*.workflow,}',
+  \ 'textile': '{*.textile,}',
+  \ 'thrift': '{*.thrift,}',
+  \ 'tmux': '{.tmux.conf,}',
+  \ 'toml': '{*.toml,Cargo.lock,Gopkg.lock,poetry.lock,Pipfile,}',
+  \ 'tptp': '{*.p,*.tptp,*.ax,}',
+  \ 'trasys': '{*.inp,}',
+  \ 'typescript': '{*.ts,}',
+  \ 'typescriptreact': '{*.tsx,}',
+  \ 'unison': '{*.u,*.uu,}',
+  \ 'v': '{*.v,}',
+  \ 'vala': '{*.vala,*.vapi,*.valadoc,}',
+  \ 'vbnet': '{*.vb,*.vbhtml,}',
+  \ 'vcl': '{*.vcl,}',
+  \ 'velocity': '{*.vm,}',
+  \ 'vmasm': '{*.mar,}',
+  \ 'vue': '{*.vue,*.wpy,}',
+  \ 'xdc': '{*.xdc,}',
+  \ 'xml': '{*.xml,*.adml,*.admx,*.ant,*.axml,*.builds,*.ccproj,*.ccxml,*.clixml,*.cproject,*.cscfg,*.csdef,*.csl,*.csproj,*.ct,*.depproj,*.dita,*.ditamap,*.ditaval,*.dll.config,*.dotsettings,*.filters,*.fsproj,*.fxml,*.glade,*.gml,*.gmx,*.grxml,*.gst,*.iml,*.ivy,*.jelly,*.jsproj,*.kml,*.launch,*.mdpolicy,*.mjml,*.mm,*.mod,*.mxml,*.natvis,*.ncl,*.ndproj,*.nproj,*.nuspec,*.odd,*.osm,*.pkgproj,*.pluginspec,*.proj,*.props,*.ps1xml,*.psc1,*.pt,*.rdf,*.resx,*.rss,*.sch,*.scxml,*.sfproj,*.shproj,*.srdf,*.storyboard,*.sublime-snippet,*.targets,*.tml,*.ts,*.tsx,*.ui,*.urdf,*.ux,*.vbproj,*.vcxproj,*.vsixmanifest,*.vssettings,*.vstemplate,*.vxml,*.wixproj,*.workflow,*.wsdl,*.wsf,*.wxi,*.wxl,*.wxs,*.x3d,*.xacro,*.xaml,*.xib,*.xlf,*.xliff,*.xmi,*.xml.dist,*.xproj,*.xsd,*.xspec,*.xul,*.zcml,*.cdxml,.classpath,.cproject,.project,App.config,NuGet.config,Settings.StyleCop,Web.Debug.config,Web.Release.config,Web.config,packages.config,}',
+  \ 'xml.twig': '{*.xml.twig,}',
+  \ 'xsl': '{*.xslt,*.xsl,}',
+  \ 'yaml': '{*.yml,*.mir,*.reek,*.rviz,*.sublime-syntax,*.syntax,*.yaml,*.yaml-tmlanguage,*.yaml.sed,*.yml.mysql,.clang-format,.clang-tidy,.gemrc,glide.lock,yarn.lock,fish_history,fish_read_history,}',
+  \ 'yaml.ansible': '{playbook.y{a,}ml,site.y{a,}ml,main.y{a,}ml,local.y{a,}ml,requirements.y{a,}ml,tasks.*.y{a,}ml,roles.*.y{a,}ml,handlers.*.y{a,}ml,}',
+  \ 'yaml.docker-compose': '{docker-compose*.yaml,docker-compose*.yml,}',
+  \ 'zephir': '{*.zep,}',
+  \ 'zig': '{*.zig,*.zir,}',
+  \ 'zir': '{*.zir,}',
+  \ 'zsh': '{*.zsh,.zshrc,.zshenv,.zlogin,.zprofile,.zlogout,}',
+  \}
+
+func! sleuth#GlobForFiletype(type)
+  return get(s:globs, a:type, '')
+endfunc
diff --git a/plugin/sleuth.vim b/plugin/sleuth.vim
new file mode 100644
index 00000000..12086173
--- /dev/null
+++ b/plugin/sleuth.vim
@@ -0,0 +1,164 @@
+" Heuristically set buffer options
+"
+" Modified version of vim-sleuth:
+"   - softtab and tabstop reduced from 8 to 2
+"   - number of considered lines reduced from 1024 to 64
+"   - maximum 6 other files are checked instead of 20
+"   - check maximum of files 2 per directory level instead of 8
+"   - maximum of 3 directory levels are checked
+"   - globs are concatenated for performance
+
+if exists("g:loaded_sleuth") || v:version < 700 || &cp
+  finish
+endif
+let g:loaded_sleuth = 1
+
+function! s:guess(lines) abort
+  let options = {}
+  let heuristics = {'spaces': 0, 'hard': 0, 'soft': 0}
+  let ccomment = 0
+  let podcomment = 0
+  let triplequote = 0
+  let backtick = 0
+  let xmlcomment = 0
+  let softtab = repeat(' ', 2)
+
+  for line in a:lines
+    if !len(line) || line =~# '^\s*$'
+      continue
+    endif
+
+    if line =~# '^\s*/\*'
+      let ccomment = 1
+    endif
+    if ccomment
+      if line =~# '\*/'
+        let ccomment = 0
+      endif
+      continue
+    endif
+
+    if line =~# '^=\w'
+      let podcomment = 1
+    endif
+    if podcomment
+      if line =~# '^=\%(end\|cut\)\>'
+        let podcomment = 0
+      endif
+      continue
+    endif
+
+    if triplequote
+      if line =~# '^[^"]*"""[^"]*$'
+        let triplequote = 0
+      endif
+      continue
+    elseif line =~# '^[^"]*"""[^"]*$'
+      let triplequote = 1
+    endif
+
+    if backtick
+      if line =~# '^[^`]*`[^`]*$'
+        let backtick = 0
+      endif
+      continue
+    elseif &filetype ==# 'go' && line =~# '^[^`]*`[^`]*$'
+      let backtick = 1
+    endif
+
+    if line =~# '^\s*<\!--'
+      let xmlcomment = 1
+    endif
+    if xmlcomment
+      if line =~# '-->'
+        let xmlcomment = 0
+      endif
+      continue
+    endif
+
+    if line =~# '^\t'
+      let heuristics.hard += 1
+    elseif line =~# '^' . softtab
+      let heuristics.soft += 1
+    endif
+    if line =~# '^  '
+      let heuristics.spaces += 1
+    endif
+    let indent = len(matchstr(substitute(line, '\t', softtab, 'g'), '^ *'))
+    if indent > 1 && (indent < 4 || indent % 2 == 0) &&
+          \ get(options, 'shiftwidth', 99) > indent
+      let options.shiftwidth = indent
+    endif
+  endfor
+
+  if heuristics.hard && !heuristics.spaces
+    return {'expandtab': 0, 'shiftwidth': &tabstop}
+  elseif heuristics.soft != heuristics.hard
+    let options.expandtab = heuristics.soft > heuristics.hard
+    if heuristics.hard
+      let options.tabstop = 2
+    endif
+  endif
+
+  return options
+endfunction
+
+function! s:apply_if_ready(options) abort
+  if !has_key(a:options, 'expandtab') || !has_key(a:options, 'shiftwidth')
+    return 0
+  else
+    for [option, value] in items(a:options)
+      call setbufvar('', '&'.option, value)
+    endfor
+    return 1
+  endif
+endfunction
+
+function! s:detect() abort
+  if &buftype ==# 'help'
+    return
+  endif
+
+  let options = s:guess(getline(1, 64))
+  if s:apply_if_ready(options)
+    return
+  endif
+  let c = 6
+  let pattern = c > 0 ? sleuth#GlobForFiletype(&filetype) : ''
+  let dir = expand('%:p:h')
+  let level = 3
+  while isdirectory(dir) && dir !=# fnamemodify(dir, ':h') && c > 0 && level > 0
+    let level -= 1
+    for neighbor in glob(dir.'/'.pattern,0,1)[0:1]
+      if neighbor !=# expand('%:p') && filereadable(neighbor)
+        call extend(options, s:guess(readfile(neighbor, '', 32)), 'keep')
+        let c -= 1
+      endif
+      if s:apply_if_ready(options)
+        let b:sleuth_culprit = neighbor
+        return
+      endif
+      if c <= 0
+        break
+      endif
+    endfor
+    if c <= 0
+      break
+    endif
+    let dir = fnamemodify(dir, ':h')
+  endwhile
+  if has_key(options, 'shiftwidth')
+    return s:apply_if_ready(extend({'expandtab': 1}, options))
+  endif
+endfunction
+
+setglobal smarttab
+
+if !exists('g:did_indent_on')
+  filetype indent on
+endif
+
+augroup polyglot
+  autocmd!
+  autocmd FileType * call s:detect()
+augroup END
diff --git a/scripts/build b/scripts/build
index 1fe148e7..2fcbe235 100755
--- a/scripts/build
+++ b/scripts/build
@@ -716,6 +716,39 @@ def detect_filetypes
   }]
 end
 
+def generate_plugins(packages)
+  FileUtils.mkdir_p('autoload/polyglot')
+
+  output = "let s:globs = {\n"
+
+  patterns = Hash.new { |h, k| h[k] = [] }
+
+  for package in packages
+    for filetype in package["filetypes"]
+      extensions = (filetype["extensions"] || []).map { |e| "*.#{e}" }
+      files = (filetype["filenames"] || []).reject { |e| e.match(/\*\*|\//) }
+      patterns[filetype["name"]].concat(extensions)
+      patterns[filetype["name"]].concat(files)
+    end
+  end
+
+  for filetype in patterns.keys.sort
+    output << "  \\ '#{filetype}': '{#{patterns[filetype].uniq.join(",")},}',\n"
+  end
+  output << "  \\}\n\n"
+
+
+  output << <<~EOS
+    func! sleuth#GlobForFiletype(type)
+      return get(s:globs, a:type, '')
+    endfunc
+  EOS
+
+
+  File.write('autoload/sleuth.vim', output)
+end
+
+
 if __FILE__ == $0
   if !ENV["DEV"]
     FileUtils.rm_rf("tmp")
@@ -725,6 +758,7 @@ if __FILE__ == $0
   download(packages)
   extract(packages)
   generate_ftdetect(packages, heuristics)
+  generate_plugins(packages)
   generate_tests(packages)
   puts(" Bye! Have a wonderful time!")