远程操作家里的mac mini进行更新的时候，突然报错：

mini:Homebrew mini$ brew update
Warning: No available formula with the name "ca-certificates".
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching for a previously deleted formula (in the last month)...
Warning: homebrew/core is shallow clone. To get its complete history, run:
git -C "$(brew --repo homebrew/core)" fetch --unshallow

Error: No previously deleted formula found.
==> Searching taps on GitHub...
Error: No formulae found in taps.
Error:
homebrew-core is a shallow clone.
To `brew update`, first run:
git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow
This command may take a few minutes to run due to the large size of the repository.
This restriction has been made on GitHub's request because updating shallow
clones is an extremely expensive operation due to the tree layout and traffic of
Homebrew/homebrew-core and Homebrew/homebrew-cask. We don't do this for you
automatically to avoid repeatedly performing an expensive unshallow operation in
CI systems (which should instead be fixed to not use shallow clones). Sorry for
the inconvenience!
于是执行 git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow ，然而执行下来还是： 
error: RPC failed; HTTP 504 curl 22 The requested URL returned error: 504 Gateway Time-out
fatal: the remote end hung up unexpectedly
然后我就用打开git trace进行查看： 
GIT_TRACE=2 git -C /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core fetch --unshallow
10:29:28.798061 exec-cmd.c:139 trace: resolved executable path from Darwin stack: /Applications/Xcode.app/Contents/Developer/usr/bin/git
10:29:28.798668 exec-cmd.c:236 trace: resolved executable dir: /Applications/Xcode.app/Contents/Developer/usr/bin
10:29:28.799328 git.c:418 trace: built-in: git fetch --unshallow
10:29:28.801482 run-command.c:643 trace: run_command: GIT_DIR=.git git-remote-https origin https://mirrors.ustc.edu.cn/homebrew-core.git
10:29:28.812513 exec-cmd.c:139 trace: resolved executable path from Darwin stack: /Applications/Xcode.app/Contents/Developer/usr/libexec/git-core/git-remote-https
10:29:28.813122 exec-cmd.c:236 trace: resolved executable dir: /Applications/Xcode.app/Contents/Developer/usr/libexec/git-core
10:29:28.929816 run-command.c:643 trace: run_command: git fetch-pack --stateless-rpc --stdin --lock-pack --include-tag --thin --depth=2147483647 https://mirrors.ustc.edu.cn/homebrew-core.git/
10:29:28.935164 exec-cmd.c:139 trace: resolved executable path from Darwin stack: /Applications/Xcode.app/Contents/Developer/usr/libexec/git-core/git
10:29:28.935863 exec-cmd.c:236 trace: resolved executable dir: /Applications/Xcode.app/Contents/Developer/usr/libexec/git-core
10:29:28.936585 git.c:418 trace: built-in: git fetch-pack --stateless-rpc --stdin --lock-pack --include-tag --thin --depth=2147483647 https://mirrors.ustc.edu.cn/homebrew-core.git/
error: RPC failed; HTTP 504 curl 22 The requested URL returned error: 504 Gateway Time-out
fatal: the remote end hung up unexpectedly
这个。。--depth=2147483647，居然这么深？
查到了网上的方案，参考在这里：记录: homebrew-core is a shallow clone - 腾讯云开发者社区-腾讯云 (tencent.com),我按上面的操作，删除了homebrew-core,homebrew-cask，再进行upgrade，果然 正常了。
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在非正常之前，做了不少操作，比如用官方的uninstall脚本清除了系统，然而也没有什么用。所幸，现在正常了。