假设我需要在修订/提交哈希标识042b84a处获取https://github.com/mozilla/gecko-dev。现在，整个仓库都是（See the size of a github repo before cloning it?）：
wget -qO- https://api.github.com/repos/mozilla/gecko-dev | grep size
# "size": 3891062, # this in kB
......这对我来说太过分了。所以，我想，我会得到一个浅层克隆 - 仅此一个就可以获得近400 MB：
git clone --depth 1 https://github.com/mozilla/gecko-dev
# remote: Counting objects: 231302, done.
# Receiving objects: 100% (231302/231302), 392.95 MiB
现在，这克隆了HEAD，我不能从这里到达042b84a，尤其是我使用的git版本1.9.1客户端（How to shallow clone a specific commit with depth 1?; How do fetch remote branch after I cloned repo with git clone --depth 1; Git: get a particular revision of a git repository with depth 1） 。显然，我能做的最好的事情就是不要使用repo（无论如何都会像完整克隆一样下载），慢慢增加深度。
我不确定“深度”是否只对应于HEAD和给定修订版之间的提交次数 - Get git sha depth on a remote branch注意到对于完整克隆，您可以这样做：
git rev-list HEAD ^042b84a --count
...所以，这意味着“深度”确实是HEAD和给定修订之间的提交次数 - 但是，没有明显的方法可以从git中的远程仓库查询。
因此，在完成克隆/深度增加之前，找到当前HEAD所需的042b84a的深度会很酷;我想也许使用命令行中的GitHub API可以提供帮助，因为它是从GitHub托管的。所以我试过了：
cd gecko-dev
wget -qO- https://api.github.com/repos/mozilla/gecko-dev/commits/042b84a | grep date
# "date": "2017-04-27T07:18:07Z"
curl -sI 'https://api.github.com/repos/mozilla/gecko-dev/commits?sha=042b84a' | grep last
# Link: <https://api.github.com/repositories/13509108/commits?sha=042b84a&page=2>; rel="next", <https://api.github.com/repositories/13509108/commits?sha=042b84a&page=17756>; rel="last"
wget -qO- 'https://api.github.com/repos/mozilla/gecko-dev/commits?sha=042b84a&page=17756' | grep '^ "sha"' | wc -l
# 5
由于参数sha为“SHA or branch to start listing commits from”，而GitHub API为“a call to list GitHub's public repositories provides paginated items in sets of 30”，此处我们有17756页，其中17756页有5个结果; - 所以，我们在042b84a和HEAD之间有17755 * 30 + 5 = 532655提交？
所以，然后我这样做 - 但是：
git fetch --progress --depth=532655
# error: RPC failed; result=18, HTTP code = 200
# fatal: The remote end hung up unexpectedly
......通话失败。
是否可以使用git客户端1.9以某种方式扩展这个浅层克隆，以包含修订版042b84a而无需克隆所有4GB数据 - 使用GitHub API提供的一些存储库数据？
编辑：有了这个，但仍然没有明确的答案。首先，532655的深度对于从现在（2018年1月）到2017年4月的提交之间的距离是可疑的。所以，我尝试查找自提交日期以来的提交：curl -sI 'https://api.github.com/repos/mozilla/gecko-dev/commits?since=2017-04-27T07:18:07Z' | grep last
# Link: <https://api.github.com/repositories/13509108/commits?since=2017-04-27T07%3A18%3A07Z&page=2>; rel="next", <https://api.github.com/repositories/13509108/commits?since=2017-04-27T07%3A18%3A07Z&page=1267>; rel="last"
wget -qO- 'https://api.github.com/repos/mozilla/gecko-dev/commits?since=2017-04-27T07:18:07Z&page=1267' | grep '^ "sha"' | wc -l
# 18
wcalc 1266*30+18
# = 37998
git fetch -v --progress --depth=37998
# POST git-upload-pack (419 bytes)
# error: RPC failed; result=18, HTTP code = 200
# fatal: The remote end hung up unexpectedly
所以，从日期开始，我们得到37998次提交或深度，但即使是那次调用也无法获取。
因此，知道提交数量至少为数千，我尝试慢慢增加：
git fetch -vvvv --progress --depth=1000 origin
# remote: Counting objects: 53595, done.
# remote: Compressing objects: 100% (24434/24434), done.
# remote: Total 53595 (delta 43532), reused 36280 (delta 28120), pack-reused 0
# Receiving objects: 100% (53595/53595), 16.14 MiB | 409.00 KiB/s, done.
# Resolving deltas: 100% (43532/43532), completed with 10563 local objects.
# From https://github.com/mozilla/gecko-dev
# = [up to date] master -> origin/master
git log --oneline | wc -l
# 7492
git fetch -vvvv --progress --depth=2000 origin
# remote: Counting objects: 140804, done.
# remote: Compressing objects: 100% (54300/54300), done.
# Receiving objects: 100% (140804/140804), 57.13 MiB | 404.00 KiB/s, done.
# remote: Total 140804 (delta 114158), reused 106827 (delta 84436), pack-reused 0
# Resolving deltas: 100% (114158/114158), completed with 20700 local objects.
# From https://github.com/mozilla/gecko-dev
# = [up to date] master -> origin/master
git log --oneline | wc -l
# 18137
......最后是循环：
i=2000; until git show 042b84a; do i=$((i+1000)); echo "depth $i"; git fetch --depth=$i ; done
# fatal: ambiguous argument '042b84a': unknown revision or path not in the working tree.
# Use '--' to separate paths from revisions, like this:
# 'git <command> [<revision>...] -- [<file>...]'
# depth 3000
# remote: Counting objects: 136434, done.
# remote: Compressing objects: 100% (47014/47014), done.
# remote: Total 136434 (delta 108858), reused 110481 (delta 86139), pack-reused 0
# Receiving objects: 100% (136434/136434), 71.36 MiB | 403.00 KiB/s, done.
# Resolving deltas: 100% (108858/108858), completed with 13997 local objects.
# fatal: ambiguous argument '042b84a': unknown revision or path not in the working tree.
# Use '--' to separate paths from revisions, like this:
# 'git <command> [<revision>...] -- [<file>...]'
# depth 4000
# remote: Counting objects: 240103, done.
# remote: Compressing objects: 100% (77811/77811), done.
# remote: Total 240103 (delta 196215), reused 195977 (delta 157920), pack-reused 0
# Receiving objects: 100% (240103/240103), 117.71 MiB | 404.00 KiB/s, done.
# Resolving deltas: 100% (196215/196215), completed with 23725 local objects.
# commit 042b84af6020b1f2d8029a0dc36ac5955b7f325f [...]
git log --oneline | wc -l
# 50871
git rev-list HEAD ^042b84a --count
# 45283
（根据对象的数量，下载大小等的增加来判断，在这种情况下看起来已经取出--depth=1000并不重要 - 在发出fetch --depth=2000时，所有先前的对象都将重新下载？）
所以，当我们042b84a时，提交git fetch --depth 4000终于出现了 - 所以显然这个提交的深度是3000＆lt;深度＆lt; = 4000？，在那个深度，我们可以计算50871个日志条目（提交？），而git rev-list HEAD ^042b84a --count报告45283（也提交？）？那么“深度”是什么，如果没有提交的数量呢？