index : cgit

cgit - CGI for Git
==================

This is an attempt to create a fast web interface for the Git SCM, using a
built-in cache to decrease server I/O pressure.


Source tree
-----------

* source/ is the C code, built inside the Git tree in vendor/git, and assets/
  holds the static files make install copies.
* custom/ holds the reference cgitrc, the web server configs in servers/, the
  Lua filters in extensions/ and in hooks/ standalone post-receive hooks that
  keep the idle column, the cache and the commit-graph current.
* tools/ holds build-release.sh for a hardened build, without Lua unless given
  lua, build-development.sh for a debug build with sanitizers, and serve.py,
  which previews the built binary on a local port and needs a cgitrc, ./cgitrc
  unless --config names another.
* tests/ is the suite make test runs.


Installation
------------

Building cgit involves building a proper version of Git. How to do this depends
on how you obtained the cgit sources.

The build needs GNU make, run as gmake on the BSDs, a C compiler and the zlib
headers, and make get-git below also needs curl or wget, and xz. zlib is the
only library cgit requires, so no development packages for OpenSSL, libcurl,
gettext or Tcl are needed. On Debian and Ubuntu that is one command.

    $ sudo apt install make gcc zlib1g-dev curl xz-utils

In a cloned cgit repository, first fetch the Git submodule.

    $ git submodule update --init

From a cgit tarball, download a proper git version instead.

    $ make get-git

With the Git tree in place, build and install cgit.

    $ make
    $ sudo make install

This installs cgit.cgi, cgit.css, cgit.js, cgit.png, favicon.ico and robots.txt
into /var/www/htdocs/cgit, and the Lua filters from custom/extensions into
/usr/local/lib/cgit/filters. The server configs in custom/servers/ look for the
binary in /usr/lib/cgit and the other five files in /usr/share/cgit instead. To
install there, put these two lines in a file named cgit.conf next to the
Makefile before running make install.

    CGIT_SCRIPT_PATH = /usr/lib/cgit
    CGIT_DATA_PATH = /usr/share/cgit

The Makefile lists the other variables cgit.conf can set, prefix among them.

make install runs the build again first, with the variables it is given, so it
needs the same ones as the build. To install the hardened binary that
tools/build-release.sh built rather than a default build, skip that rebuild with
make's -o option.

    $ sudo make -o all install

On a musl system such as Alpine, Git's code also needs the Linux kernel headers,
packaged there as linux-headers, and its bundled regex in place of musl's, which
lacks REG_STARTEND. make install and make test take the same setting.

    $ make NO_REGEX=YesPlease

Lua is optional and only powers the lua: filter extensions, the filters in
custom/extensions/. A plain build auto-detects a Lua through pkg-config,
preferring LuaJIT, and falls back to a Lua-less binary when none is found. On
Debian and Ubuntu, detection needs pkg-config and a development package such as
libluajit-5.1-dev or liblua5.4-dev. To pin an implementation, name its
pkg-config module.

    $ make LUA_PKGCONFIG=lua5.4

Acceptable LUA_PKGCONFIG values include "luajit", "lua", "lua5.5", "lua5.4",
"lua5.3", "lua5.2" and "lua5.1". To build without Lua, so the binary needs no
Lua at runtime, turn it off.

    $ make NO_LUA=1

A binary built this way still runs every exec: filter, but a filter named with
the lua: prefix has no interpreter to run in, so it is refused with an error on
every page until the setting is taken out of cgitrc. make test builds this
variant as well, into build/nolua, and checks it the same way.


Quick start
-----------

cgit is a CGI program that reads its options and its list of repositories from
/etc/cgitrc. custom/cgitrc is a fully commented starting point with every option
at its default, and MANUAL.txt documents each option in full. With cgit
installed as above, copy custom/cgitrc to /etc/cgitrc and point it at the
repositories, with scan-path for every repository below one directory or a
repo.url and a repo.path line for each. They have to be readable by the account
the web server runs cgit as, www-data on Debian, since a scanned repository it
cannot read is left off the index with only a line in the error log.

Complete, commented configurations for nginx, Apache and lighttpd live in
custom/servers/, each explaining how that server routes requests to the binary
and serves the static assets off disk. Install the one for your server.

The cache is off until cache-size is set above 0, as in cache-size=1000 placed
above scan-path. Its directory has to exist first, owned by the same account
and closed to the others.

    $ sudo install -d -o www-data -m 0700 /var/cache/cgit

From a shell, --version names the build and whether it has Lua. --nohttp
--query= prints the page for a query string, reading /etc/cgitrc or the file
CGIT_CONFIG names, and --scan-path= prints what a scan of a directory finds as
cgitrc lines, without reading cgitrc. Run as the web server's account, a page
meets its permissions and prints on stderr what the error log would get.

    $ /usr/lib/cgit/cgit.cgi --version
    $ sudo -u www-data /usr/lib/cgit/cgit.cgi --nohttp --query=url=demo/log


Customisation
-------------

Every page is one document with the same skeleton, so a site stylesheet or
script added through the css and js options has stable hooks to work with.

* The root is div#cgit. It carries data-page with the page name, summary, log,
  tree and so on, and data-repo with the repository url on repository pages,
  so a rule can target one page or one repository. In embedded mode it also
  carries the class cgit-embedded.
* Inside it sit header#header, nav.tabs with the search form, nav.path for the
  breadcrumb, main.content and footer.footer. Each nav, listing and option form
  carries an aria-label, and the active tab and the current pager link carry
  aria-current.
* Every listing is a table.list with a second class naming it, repolist,
  summary, refs, log, tree or clone, the last holding the clone urls of an
  empty repository. Each section of a listing is a tbody named repos,
  branches, tags, log, clone or tree, and each row carries its kind, repo,
  branch, tag, commit, dir, blob, link or mod. A file row's link also carries
  ext- followed by the file extension.
* The commit and tag pages use table.commit-info, the trailer table is
  table.commit-trailers, the diffstat is table.diffstat and each file of a diff
  is div.file, or tbody.file in the side-by-side view, with the path in
  data-path. The blob and blame pages open with div.blob-header.
* Relative ages are time elements with an age-* class and the timestamp in
  data-ut, while a date shown in full is a plain time element. Line numbers are
  anchors named n followed by the line, while enable-tree-linenumbers is on.
  A character in a file that a browser would start a new line at, though git
  does not, such as a carriage return with no line feed after it, is shown as
  an escape sequence in span.escape.
* The bundled auth filters write their login form as form.login, with
  p.login-error above it after a failed login.
* Colours, fonts and metrics are custom properties on div#cgit, so a theme can
  redefine those alone. Every rule in cgit.css starts with div#cgit, apart from
  the background and margins it sets on html.cgit-standalone, the class of the
  document cgit writes when it is not embedded. A rule of your own needs the
  div#cgit prefix to win.
* The script exposes window.cgit.updateAges and window.cgit.highlightLines for
  a page that changes the rows or the lines after load.

A theme that only wants a colour change is a few lines.

    div#cgit {
      --link: light-dark(#7a1f1f, #f0a0a0);
      --font-sans: Georgia, serif;
    }

    div#cgit[data-page='log'] table.list tr.commit:hover {
      background: var(--surface);
    }

tests/t0005-markup.sh checks that every hook named here is still emitted.


Filter extensions
-----------------

The optional Lua filters in custom/extensions/ mostly need extra Lua modules,
and each script's header lists the exact install commands for its own.

* The auth filters, auth-file.lua and auth-inline.lua, need luaossl and
  luaposix.
* The email filters, email-gravatar.lua and email-libravatar.lua, need luaossl.
* The syntax highlighter, syntax-highlight.lua, needs lpeg and a Scintillua
  recent enough to have detect().
* The about-page renderer, about-render.lua, needs lpeg for markdown and man
  pages. Plain text needs only Lua.
* link-commits.lua and link-trailers.lua need nothing beyond Lua itself.

On Lua 5.5 the auth and email filters need luaossl 20260910 or later, since
earlier builds fail to load there.

The auth filters create the secret that signs their cookies on first use, as
/var/lib/cgit/auth-secret, but not its directory. Make that by hand, owned by
the account the web server runs cgit as, with mode 0700.


Urls and query parameters
-------------------------

cgit serves every page from one CGI program, so a url names the repository, the
page and a path inside that page. There are two forms and they carry the same
information. The one cgit's own links take is a path, written as
/<repo>/<page>/<path> with anything else as a query string. In the other the
whole request lives in the query string as ?url=<repo>/<page>/<path>.

The page name is the second element and is one of about, atom, blame, blob,
commit, diff, log, patch, plain, rawdiff, refs, snapshot, stats, summary, tag or
tree. Leaving it out gives the repository summary, and leaving the repository
out as well gives the index of repositories. Everything after the page name is
the path argument, so /demo/tree/src/main.c asks for the tree page at
src/main.c. A repository whose name contains a character that is special in a
url has it percent-encoded, and a plus sign has to be written %2b because a bare
plus decodes to a space.

A page of the site itself has no repository in front of it, so p names it
instead, as in ?p=about. These pages are about, which shows root-readme,
repolist, the index under its own name, login, which an auth filter answers, and
ls_cache, which lists the cache when enable-cache-list allows it.

Every parameter is optional. The pages column names the pages that read each
one, where a value of all marks the few not tied to particular pages.

+----------+----------------------+--------------------------------------------+
| param    | pages                | description                                |
+----------+----------------------+--------------------------------------------+
| url      | all                  | repository, page and path in one value     |
| r        | all                  | the repository on its own, in place of url |
| p        | all                  | the page on its own, in place of url       |
| h        | all                  | the branch or ref to read                  |
| id       | all                  | pin the page to one commit or object       |
| id2      | diff patch rawdiff   | second object of a diff, paired with id    |
| ofs      | index log refs       | offset into a paged listing                |
| ofs      | stats                | authors to show, -1 for all of them        |
| path     | all                  | restrict the page to one path              |
| q        | index log            | the search term, matched literally         |
| qt       | log                  | one of grep, author, committer or range    |
| s        | index                | sort key for the listing                   |
| showmsg  | log                  | show full commit messages                  |
| period   | stats                | the statistics window, one of w, m, q or y |
| dt       | diff commit          | 0 unified, 1 side-by-side or 2 stat only   |
| ss       | diff commit          | shorthand for the side-by-side diff        |
| all      | atom                 | include every ref rather than one branch   |
| context  | diff commit          | lines of context around a diff hunk        |
| ignorews | diff commit          | ignore whitespace when diffing             |
| follow   | log                  | follow a single path across renames        |
+----------+----------------------+--------------------------------------------+

A number out of range is clamped rather than refused, ofs to 100000 and context
to 40 lines, and q is cut at 512 characters.

A few endpoints are not ordinary pages. The snapshot page takes a filename
rather than a ref, so /demo/snapshot/demo-1.0.tar.gz names both the ref and the
archive format through the suffix, and the formats on offer are set by the
snapshots option. The plain page serves a blob as its own bytes under headers
that stop a browser treating repository content as markup. The atom page is a
feed rather than a page and accepts h, path and all. The clone endpoints under
info and objects implement the dumb HTTP protocol and are only present when http
clone is enabled.

A url fragment can address lines inside a file. While enable-tree-linenumbers is
on, as it is by default, the tree and blame pages give every line an anchor
named n followed by its number, so #n17 jumps to line 17 and highlights it, and
a range written #n17-n24 highlights the whole run and scrolls it into view.

Some worked examples, in the url= form.

    ?url=                              the repository index
    ?url=demo                          summary for the demo repository
    ?url=demo/log&h=next               log of the next branch
    ?url=demo/log&qt=author&q=alice    commits authored by alice
    ?url=demo/tree/src&h=v1.0          the src directory at tag v1.0
    ?url=demo/commit&id=v1.0           one commit, pinned to a tag
    ?url=demo/diff&id=main&id2=next    diff between two branches
    ?url=demo/plain/README.md          the raw bytes of one file
    ?url=demo/atom&h=main              the commit feed for a branch


Credits
-------

cgit was created by Lars Hjemli and maintained upstream for many years, most
recently by Jason A. Donenfeld. This repository is an independent fork that
builds on their work. They are not maintainers of this fork and are not
responsible for it.

cgit is built on Git, which Linus Torvalds created and Junio C Hamano maintains
with the help of many contributors. Git's own code, bundled in vendor/git, is
compiled into cgit and reads every repository that cgit shows.