git - 如何通过 http 使用智能协议(protocol)(原始)获取 git 对象？

Question

我正在尝试通过 http 使用 git 智能协议(protocol)从 github.com/git/git 获取标签“v2.4.2”的注释。

//获取引用

curl -H "User-Agent: git/1.8.1" -v  https://github.com/git/git/info/refs?service=git-upload-pack

返回引用:

.....
003e2be062dfcfd1fd4aca132ec02a40b56f63776202 refs/tags/v2.4.1
0041aaa7e0d7f8f003c0c8ab34f959083f6d191d44ca refs/tags/v2.4.1^{}
003e29932f3915935d773dc8d52c292cadd81c81071d refs/tags/v2.4.2
00419eabf5b536662000f79978c4d1b6e4eff5c8d785 refs/tags/v2.4.2^{}

//发起上传包请求

printf "0031want 00419eabf5b536662000f79978c4d1b6e4eff5c8d785\n0024have 003e2be062dfcfd1fd4aca132ec02a40b56f63776202\n0000" | curl -H "User-Agent: git/1.8.1" -v  -d @- https://github.com/git/git/git-upload-pack -H "Content-Type: application/x-git-upload-pack-request" --trace-ascii /dev/stdout

这不会返回任何内容。我想知道请求中有什么问题(即我计算错了十六进制吗？)

Warning: --trace-ascii overrides an earlier trace/verbose option
== Info: Hostname was NOT found in DNS cache
== Info:   Trying 192.30.252.130...
== Info: Connected to github.com (192.30.252.130) port 443 (#0)
== Info: TLS 1.2 connection using TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
== Info: Server certificate: github.com
== Info: Server certificate: DigiCert SHA2 Extended Validation Server CA
== Info: Server certificate: DigiCert High Assurance EV Root CA
=> Send header, 170 bytes (0xaa)
0000: POST /git/git/git-upload-pack HTTP/1.1
0028: Host: github.com
003a: Accept: */*
0047: User-Agent: git/1.8.1
005e: Content-Type: application/x-git-upload-pack-request
0093: Content-Length: 110
00a8: 
=> Send data, 110 bytes (0x6e)
0000: 0031want 00419eabf5b536662000f79978c4d1b6e4eff5c8d7850024have 00
0040: 3e2be062dfcfd1fd4aca132ec02a40b56f637762020000
== Info: upload completely sent off: 110 out of 110 bytes
<= Recv header, 17 bytes (0x11)
0000: HTTP/1.1 200 OK
== Info: Server GitHub Babel 2.0 is not blacklisted
<= Recv header, 26 bytes (0x1a)
0000: Server: GitHub Babel 2.0
<= Recv header, 52 bytes (0x34)
0000: Content-Type: application/x-git-upload-pack-result
<= Recv header, 28 bytes (0x1c)
0000: Transfer-Encoding: chunked
<= Recv header, 40 bytes (0x28)
0000: Expires: Fri, 01 Jan 1980 00:00:00 GMT
<= Recv header, 18 bytes (0x12)
0000: Pragma: no-cache
<= Recv header, 53 bytes (0x35)
0000: Cache-Control: no-cache, max-age=0, must-revalidate
<= Recv header, 23 bytes (0x17)
0000: Vary: Accept-Encoding
<= Recv header, 2 bytes (0x2)
0000: 
<= Recv data, 5 bytes (0x5)
0000: 0
0003: 
== Info: Connection #0 to host github.com left intact

我为什么要尝试这个？

• 我没有文件系统的写权限
• 避免获取不必要的数据(即提交)
• 标准 API/协议(protocol)

Answer 1

提交十六进制

您没有错误计算十六进制，但您没有传递正确的值。请记住 smart protocol 中的每一行前面是长度计数:

<length><data>

所以对于看起来像这样的一行:

00419eabf5b536662000f79978c4d1b6e4eff5c8d785 refs/tags/v2.4.2^{}

您需要丢弃前四个字符，这使实际提交成为十六进制:

9eabf5b536662000f79978c4d1b6e4eff5c8d785

请求格式

当 POST 请求时，have 和 want 行应该用换行符分隔，但是如果你看一下在 curl 的输出中，您可以看到没有换行符:

=> Send data, 110 bytes (0x6e)
0000: 0031want 00419eabf5b536662000f79978c4d1b6e4eff5c8d7850024have 00
0040: 3e2be062dfcfd1fd4aca132ec02a40b56f637762020000

您需要使用--data-binary 而不是--data:

--data-binary @-

您需要在这些行前面加上长度计数，并且您需要以包含 0000 的行结束:

0032want 9eabf5b536662000f79978c4d1b6e4eff5c8d785
0032have 2be062dfcfd1fd4aca132ec02a40b56f63776202
0000

调试技巧

如果您想从 git 获取大量调试信息以准确查看它来回发送的内容，您可以在您的环境中设置 GIT_TRACE_PACKET=1。

这就是他写的全部内容

即使提供了上述信息，我自己也无法得到回复，但我认为这会有所帮助。

更新

所以，这很有趣。

我在本地设置了一个 git 服务器(使用 git http-backend 和 thttpd )，然后运行 ​​tcpdump 来获取 git 产生的流量远程更新操作。事实证明，您需要使用空命令分隔 want 和 have 指令，即 0000(没有换行符，因为长度也编码换行符)。即:

<length>want <commitid><newline>
0000<length>have <commitid><newline>
<length>done

例如:

0032want 9eabf5b536662000f79978c4d1b6e4eff5c8d785
00000032have 2be062dfcfd1fd4aca132ec02a40b56f63776202
0009done

这给了我:

0000: POST /git/git/git-upload-pack HTTP/1.1
0028: Host: github.com
003a: Accept: */*
0047: Content-type: application/x-git-upload-pack-request
007c: User-agent: git/1.8
0091: Content-Length: 113
00a6: 
=> Send data, 113 bytes (0x71)
0000: 0032want 9eabf5b536662000f79978c4d1b6e4eff5c8d785.00000032have 2
0040: be062dfcfd1fd4aca132ec02a40b56f63776202.0009done.
== Info: upload completely sent off: 113 out of 113 bytes
<= Recv header, 17 bytes (0x11)
0000: HTTP/1.1 200 OK
<= Recv header, 26 bytes (0x1a)
0000: Server: GitHub Babel 2.0
<= Recv header, 52 bytes (0x34)
0000: Content-Type: application/x-git-upload-pack-result
<= Recv header, 28 bytes (0x1c)
0000: Transfer-Encoding: chunked
<= Recv header, 40 bytes (0x28)
0000: Expires: Fri, 01 Jan 1980 00:00:00 GMT
<= Recv header, 18 bytes (0x12)
0000: Pragma: no-cache
<= Recv header, 53 bytes (0x35)
0000: Cache-Control: no-cache, max-age=0, must-revalidate
<= Recv header, 23 bytes (0x17)
0000: Vary: Accept-Encoding
<= Recv header, 2 bytes (0x2)
0000: 
<= Recv data, 4 bytes (0x4)
0000: 31
<= Recv data, 51 bytes (0x33)
0000: 0031ACK 2be062dfcfd1fd4aca132ec02a40b56f63776202.
<= Recv data, 6 bytes (0x6)
0000: 1fff
<= Recv data, 1370 bytes (0x55a)
0000: PACK.......[..x...An.0...z.?`..d.*..@..z..(.tu......>~B.....]..8
0040: 2...j).OQ}..#.....'......[..8K..t..,%.S..u..@l..XT...o......'...
[....]

双倍奖励更新

您可以使用 git unpack-objects 命令来提取包文件。正如您从上面的跟踪中看到的那样，您首先得到一个长度编码的响应(
0031ACK 2be062dfcfd1fd4aca132ec02a40b56f63776202) 后跟包数据，因此您需要丢弃第一行:

$ git init tmprepo
$ cd temprepo
$ tail -n +2 output_from_curl | git unpack-objects
Unpacking objects: 100% (91/91), done.
$ find .git/objects -type f | head -3
$ git cat-file -p dc940e63c453199dd9a7285533fbf2355bab03d1
/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This handles basic git sha1 object files - packing, unpacking,
 * creation etc.
 */
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