Merge branch 'jk/http-server-protocol-versions'

Taking advantage of the CGI interface, http-backend has been
updated to enable protocol v2 automatically when the other side
asks for it.

* jk/http-server-protocol-versions:
  docs/protocol-v2: point readers transport config discussion
  docs/git: discuss server-side config for GIT_PROTOCOL
  docs/http-backend: mention v2 protocol
  http-backend: handle HTTP_GIT_PROTOCOL CGI variable
  t5551: test v2-to-v0 http protocol fallback
pull/1095/head
Junio C Hamano 1 year ago
commit cabb41d0f6
  1. 26
      Documentation/git-http-backend.txt
  2. 8
      Documentation/git-upload-pack.txt
  3. 15
      Documentation/git.txt
  4. 8
      Documentation/technical/protocol-v2.txt
  5. 4
      http-backend.c
  6. 7
      t/lib-httpd/apache.conf
  7. 9
      t/t5551-http-fetch-smart.sh

@ -16,7 +16,9 @@ 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.
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
@ -77,6 +79,18 @@ Apache 2.x::
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=$0
----------------------------------------------------------------
+
To enable anonymous read access but authenticated write access,
@ -264,6 +278,16 @@ a repository with an extremely large number of refs. The value can be
specified with a unit (e.g., `100M` for 100 megabytes). The default is
10 megabytes.
Clients may probe for optional protocol capabilities (like the v2
protocol) using the `Git-Protocol` HTTP header. In order to support
these, the contents of that header must appear in the `GIT_PROTOCOL`
environment variable. Most webservers will pass this header to the CGI
via the `HTTP_GIT_PROTOCOL` variable, and `git-http-backend` will
automatically copy that to `GIT_PROTOCOL`. However, some webservers may
be more selective about which headers they'll pass, in which case they
need to be configured explicitly (see the mention of `Git-Protocol` in
the Apache config from the earlier EXAMPLES section).
The backend process sets GIT_COMMITTER_NAME to '$REMOTE_USER' and
GIT_COMMITTER_EMAIL to '$\{REMOTE_USER}@http.$\{REMOTE_ADDR\}',
ensuring that any reflogs created by 'git-receive-pack' contain some

@ -48,6 +48,14 @@ OPTIONS
<directory>::
The repository to sync from.
ENVIRONMENT
-----------
`GIT_PROTOCOL`::
Internal variable used for handshaking the wire protocol. Server
admins may need to configure some transports to allow this
variable to be passed. See the discussion in linkgit:git[1].
SEE ALSO
--------
linkgit:gitnamespaces[7]

@ -894,6 +894,21 @@ for full details.
Contains a colon ':' separated list of keys with optional values
'key[=value]'. Presence of unknown keys and values must be
ignored.
+
Note that servers may need to be configured to allow this variable to
pass over some transports. It will be propagated automatically when
accessing local repositories (i.e., `file://` or a filesystem path), as
well as over the `git://` protocol. For git-over-http, it should work
automatically in most configurations, but see the discussion in
linkgit:git-http-backend[1]. For git-over-ssh, the ssh server may need
to be configured to allow clients to pass this variable (e.g., by using
`AcceptEnv GIT_PROTOCOL` with OpenSSH).
+
This configuration is optional. If the variable is not propagated, then
clients will fall back to the original "v0" protocol (but may miss out
on some performance improvements or features). This variable currently
only affects clones and fetches; it is not yet used for pushes (but may
be in the future).
`GIT_OPTIONAL_LOCKS`::
If set to `0`, Git will complete any requested operation without

@ -42,7 +42,8 @@ Initial Client Request
In general a client can request to speak protocol v2 by sending
`version=2` through the respective side-channel for the transport being
used which inevitably sets `GIT_PROTOCOL`. More information can be
found in `pack-protocol.txt` and `http-protocol.txt`. In all cases the
found in `pack-protocol.txt` and `http-protocol.txt`, as well as the
`GIT_PROTOCOL` definition in `git.txt`. In all cases the
response from the server is the capability advertisement.
Git Transport
@ -58,6 +59,8 @@ SSH and File Transport
When using either the ssh:// or file:// transport, the GIT_PROTOCOL
environment variable must be set explicitly to include "version=2".
The server may need to be configured to allow this environment variable
to pass.
HTTP Transport
~~~~~~~~~~~~~~
@ -84,6 +87,9 @@ Subsequent requests are then made directly to the service
Uses the `--http-backend-info-refs` option to
linkgit:git-upload-pack[1].
The server may need to be configured to pass this header's contents via
the `GIT_PROTOCOL` variable. See the discussion in `git-http-backend.txt`.
Capability Advertisement
------------------------

@ -739,6 +739,7 @@ static int bad_request(struct strbuf *hdr, const struct service_cmd *c)
int cmd_main(int argc, const char **argv)
{
char *method = getenv("REQUEST_METHOD");
const char *proto_header;
char *dir;
struct service_cmd *cmd = NULL;
char *cmd_arg = NULL;
@ -789,6 +790,9 @@ int cmd_main(int argc, const char **argv)
http_config();
max_request_buffer = git_env_ulong("GIT_HTTP_MAX_REQUEST_BUFFER",
max_request_buffer);
proto_header = getenv("HTTP_GIT_PROTOCOL");
if (proto_header)
setenv(GIT_PROTOCOL_ENVIRONMENT, proto_header, 0);
cmd->imp(&hdr, cmd_arg);
return 0;

@ -81,8 +81,6 @@ PassEnv GIT_TRACE
PassEnv GIT_CONFIG_NOSYSTEM
PassEnv GIT_TEST_SIDEBAND_ALL
SetEnvIf Git-Protocol ".*" GIT_PROTOCOL=$0
Alias /dumb/ www/
Alias /auth/dumb/ www/auth/dumb/
@ -117,6 +115,11 @@ Alias /auth/dumb/ www/auth/dumb/
SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
SetEnv GIT_HTTP_EXPORT_ALL
</LocationMatch>
<LocationMatch /smart_v0/>
SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
SetEnv GIT_HTTP_EXPORT_ALL
SetEnv GIT_PROTOCOL
</LocationMatch>
ScriptAlias /smart/incomplete_length/git-upload-pack incomplete-length-upload-pack-v2-http.sh/
ScriptAlias /smart/incomplete_body/git-upload-pack incomplete-body-upload-pack-v2-http.sh/
ScriptAliasMatch /error_git_upload_pack/(.*)/git-upload-pack error.sh/

@ -558,4 +558,13 @@ test_expect_success 'http auth forgets bogus credentials' '
expect_askpass both user@host
'
test_expect_success 'client falls back from v2 to v0 to match server' '
GIT_TRACE_PACKET=$PWD/trace \
GIT_TEST_PROTOCOL_VERSION=2 \
git clone $HTTPD_URL/smart_v0/repo.git repo-v0 &&
# check for v0; there the HEAD symref is communicated in the capability
# line; v2 uses a different syntax on each ref advertisement line
grep symref=HEAD:refs/heads/ trace
'
test_done

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