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git-commit-vandalism/Documentation/git-http-backend.txt
Jeff King 295d81b9e4 docs/http-backend: mention v2 protocol 
Historically there was a little bit of configuration needed at the
webserver level in order to get the client's v2 protocol probes to Git.
But when we introduced the v2 protocol, we never documented these.

As of the previous commit, this should mostly work out of the box
without any explicit configuration. But it's worth documenting this to
make it clear how we expect it to work, especially in the face of
webservers which don't provide all headers over the CGI interface. Or
anybody who runs across this documentation but has an older version of
Git (or _used_ to have an older version, and wonders why they still have
a SetEnvIf line in their Apache config and whether it's still
necessary).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-09-10 15:34:59 -07:00

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git-http-backend(1)
===================
NAME
----
git-http-backend - Server side implementation of Git over HTTP
SYNOPSIS
--------
[verse]
'git http-backend'
DESCRIPTION
-----------
A simple CGI program to serve the contents of a Git repository to Git
clients accessing the repository over http:// and https:// protocols.
The program supports clients fetching using both the smart HTTP protocol
and the backwards-compatible dumb HTTP protocol, as well as clients
pushing using the smart HTTP protocol. It also supports Git's
more-efficient "v2" protocol if properly configured; see the
discussion of `GIT_PROTOCOL` in the ENVIRONMENT section below.
It verifies that the directory has the magic file
"git-daemon-export-ok", and it will refuse to export any Git directory
that hasn't explicitly been marked for export this way (unless the
`GIT_HTTP_EXPORT_ALL` environmental variable is set).
By default, only the `upload-pack` service is enabled, which serves
'git fetch-pack' and 'git ls-remote' clients, which are invoked from
'git fetch', 'git pull', and 'git clone'. If the client is authenticated,
the `receive-pack` service is enabled, which serves 'git send-pack'
clients, which is invoked from 'git push'.
SERVICES
--------
These services can be enabled/disabled using the per-repository
configuration file:
http.getanyfile::
This serves Git clients older than version 1.6.6 that are unable to use the
upload pack service. When enabled, clients are able to read
any file within the repository, including objects that are
no longer reachable from a branch but are still present.
It is enabled by default, but a repository can disable it
by setting this configuration item to `false`.
http.uploadpack::
This serves 'git fetch-pack' and 'git ls-remote' clients.
It is enabled by default, but a repository can disable it
by setting this configuration item to `false`.
http.receivepack::
This serves 'git send-pack' clients, allowing push. It is
disabled by default for anonymous users, and enabled by
default for users authenticated by the web server. It can be
disabled by setting this item to `false`, or enabled for all
users, including anonymous users, by setting it to `true`.
URL TRANSLATION
---------------
To determine the location of the repository on disk, 'git http-backend'
concatenates the environment variables PATH_INFO, which is set
automatically by the web server, and GIT_PROJECT_ROOT, which must be set
manually in the web server configuration. If GIT_PROJECT_ROOT is not
set, 'git http-backend' reads PATH_TRANSLATED, which is also set
automatically by the web server.
EXAMPLES
--------
All of the following examples map `http://$hostname/git/foo/bar.git`
to `/var/www/git/foo/bar.git`.
Apache 2.x::
Ensure mod_cgi, mod_alias, and mod_env are enabled, set
GIT_PROJECT_ROOT (or DocumentRoot) appropriately, and
create a ScriptAlias to the CGI:
+
----------------------------------------------------------------
SetEnv GIT_PROJECT_ROOT /var/www/git
SetEnv GIT_HTTP_EXPORT_ALL
ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/
# This is not strictly necessary using Apache and a modern version of
# git-http-backend, as the webserver will pass along the header in the
# environment as HTTP_GIT_PROTOCOL, and http-backend will copy that into
# GIT_PROTOCOL. But you may need this line (or something similar if you
# are using a different webserver), or if you want to support older Git
# versions that did not do that copying.
#
# Having the webserver set up GIT_PROTOCOL is perfectly fine even with
# modern versions (and will take precedence over HTTP_GIT_PROTOCOL,
# which means it can be used to override the client's request).
SetEnvIf Git-Protocol ".*" GIT_PROTOCOL=$0
----------------------------------------------------------------
+
To enable anonymous read access but authenticated write access,
require authorization for both the initial ref advertisement (which we
detect as a push via the service parameter in the query string), and the
receive-pack invocation itself:
+
----------------------------------------------------------------
RewriteCond %{QUERY_STRING} service=git-receive-pack [OR]
RewriteCond %{REQUEST_URI} /git-receive-pack$
RewriteRule ^/git/ - [E=AUTHREQUIRED:yes]
<LocationMatch "^/git/">
Order Deny,Allow
Deny from env=AUTHREQUIRED
AuthType Basic
AuthName "Git Access"
Require group committers
Satisfy Any
...
</LocationMatch>
----------------------------------------------------------------
+
If you do not have `mod_rewrite` available to match against the query
string, it is sufficient to just protect `git-receive-pack` itself,
like:
+
----------------------------------------------------------------
<LocationMatch "^/git/.*/git-receive-pack$">
AuthType Basic
AuthName "Git Access"
Require group committers
...
</LocationMatch>
----------------------------------------------------------------
+
In this mode, the server will not request authentication until the
client actually starts the object negotiation phase of the push, rather
than during the initial contact. For this reason, you must also enable
the `http.receivepack` config option in any repositories that should
accept a push. The default behavior, if `http.receivepack` is not set,
is to reject any pushes by unauthenticated users; the initial request
will therefore report `403 Forbidden` to the client, without even giving
an opportunity for authentication.
+
To require authentication for both reads and writes, use a Location
directive around the repository, or one of its parent directories:
+
----------------------------------------------------------------
<Location /git/private>
AuthType Basic
AuthName "Private Git Access"
Require group committers
...
</Location>
----------------------------------------------------------------
+
To serve gitweb at the same url, use a ScriptAliasMatch to only
those URLs that 'git http-backend' can handle, and forward the
rest to gitweb:
+
----------------------------------------------------------------
ScriptAliasMatch \
"(?x)^/git/(.*/(HEAD | \
info/refs | \
objects/(info/[^/]+ | \
[0-9a-f]{2}/[0-9a-f]{38} | \
pack/pack-[0-9a-f]{40}\.(pack|idx)) | \
git-(upload|receive)-pack))$" \
/usr/libexec/git-core/git-http-backend/$1
ScriptAlias /git/ /var/www/cgi-bin/gitweb.cgi/
----------------------------------------------------------------
+
To serve multiple repositories from different linkgit:gitnamespaces[7] in a
single repository:
+
----------------------------------------------------------------
SetEnvIf Request_URI "^/git/([^/]*)" GIT_NAMESPACE=$1
ScriptAliasMatch ^/git/[^/]*(.*) /usr/libexec/git-core/git-http-backend/storage.git$1
----------------------------------------------------------------
Accelerated static Apache 2.x::
Similar to the above, but Apache can be used to return static
files that are stored on disk. On many systems this may
be more efficient as Apache can ask the kernel to copy the
file contents from the file system directly to the network:
+
----------------------------------------------------------------
SetEnv GIT_PROJECT_ROOT /var/www/git
AliasMatch ^/git/(.*/objects/[0-9a-f]{2}/[0-9a-f]{38})$ /var/www/git/$1
AliasMatch ^/git/(.*/objects/pack/pack-[0-9a-f]{40}.(pack|idx))$ /var/www/git/$1
ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/
----------------------------------------------------------------
+
This can be combined with the gitweb configuration:
+
----------------------------------------------------------------
SetEnv GIT_PROJECT_ROOT /var/www/git
AliasMatch ^/git/(.*/objects/[0-9a-f]{2}/[0-9a-f]{38})$ /var/www/git/$1
AliasMatch ^/git/(.*/objects/pack/pack-[0-9a-f]{40}.(pack|idx))$ /var/www/git/$1
ScriptAliasMatch \
"(?x)^/git/(.*/(HEAD | \
info/refs | \
objects/info/[^/]+ | \
git-(upload|receive)-pack))$" \
/usr/libexec/git-core/git-http-backend/$1
ScriptAlias /git/ /var/www/cgi-bin/gitweb.cgi/
----------------------------------------------------------------
Lighttpd::
Ensure that `mod_cgi`, `mod_alias`, `mod_auth`, `mod_setenv` are
loaded, then set `GIT_PROJECT_ROOT` appropriately and redirect
all requests to the CGI:
+
----------------------------------------------------------------
alias.url += ( "/git" => "/usr/lib/git-core/git-http-backend" )
$HTTP["url"] =~ "^/git" {
cgi.assign = ("" => "")
setenv.add-environment = (
"GIT_PROJECT_ROOT" => "/var/www/git",
"GIT_HTTP_EXPORT_ALL" => ""
)
}
----------------------------------------------------------------
+
To enable anonymous read access but authenticated write access:
+
----------------------------------------------------------------
$HTTP["querystring"] =~ "service=git-receive-pack" {
include "git-auth.conf"
}
$HTTP["url"] =~ "^/git/.*/git-receive-pack$" {
include "git-auth.conf"
}
----------------------------------------------------------------
+
where `git-auth.conf` looks something like:
+
----------------------------------------------------------------
auth.require = (
"/" => (
"method" => "basic",
"realm" => "Git Access",
"require" => "valid-user"
)
)
# ...and set up auth.backend here
----------------------------------------------------------------
+
To require authentication for both reads and writes:
+
----------------------------------------------------------------
$HTTP["url"] =~ "^/git/private" {
include "git-auth.conf"
}
----------------------------------------------------------------
ENVIRONMENT
-----------
'git http-backend' relies upon the `CGI` environment variables set
by the invoking web server, including:
* PATH_INFO (if GIT_PROJECT_ROOT is set, otherwise PATH_TRANSLATED)
* REMOTE_USER
* REMOTE_ADDR
* CONTENT_TYPE
* QUERY_STRING
* REQUEST_METHOD
The `GIT_HTTP_EXPORT_ALL` environmental variable may be passed to
'git-http-backend' to bypass the check for the "git-daemon-export-ok"
file in each repository before allowing export of that repository.
The `GIT_HTTP_MAX_REQUEST_BUFFER` environment variable (or the
`http.maxRequestBuffer` config variable) may be set to change the
largest ref negotiation request that git will handle during a fetch; any
fetch requiring a larger buffer will not succeed. This value should not
normally need to be changed, but may be helpful if you are fetching from
a repository with an extremely large number of refs. The value can be
specified with a unit (e.g., `100M` for 100 megabytes). The default is
10 megabytes.
Clients may probe for optional protocol capabilities (like the v2
protocol) using the `Git-Protocol` HTTP header. In order to support
these, the contents of that header must appear in the `GIT_PROTOCOL`
environment variable. Most webservers will pass this header to the CGI
via the `HTTP_GIT_PROTOCOL` variable, and `git-http-backend` will
automatically copy that to `GIT_PROTOCOL`. However, some webservers may
be more selective about which headers they'll pass, in which case they
need to be configured explicitly (see the mention of `Git-Protocol` in
the Apache config from the earlier EXAMPLES section).
The backend process sets GIT_COMMITTER_NAME to '$REMOTE_USER' and
GIT_COMMITTER_EMAIL to '$\{REMOTE_USER}@http.$\{REMOTE_ADDR\}',
ensuring that any reflogs created by 'git-receive-pack' contain some
identifying information of the remote user who performed the push.
All `CGI` environment variables are available to each of the hooks
invoked by the 'git-receive-pack'.
GIT
---
Part of the linkgit:git[1] suite
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