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ツリーオブジェクトに格納されているSHA1ハッシュ（によって返されるgit ls-tree）が、ファイルコンテンツのSHA1ハッシュ（によって返される）と一致しませんsha1sum。

$ git cat-file blob 4716ca912495c805b94a88ef6dc3fb4aff46bf3c | sha1sum
de20247992af0f949ae8df4fa9a37e4a03d7063e  -

Gitはファイルハッシュをどのように計算しますか？ハッシュを計算する前にコンテンツを圧縮しますか？

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5 に答える 5

133

Gitは、オブジェクトの前に「blob」、長さ（人間が読み取れる整数として）、NUL文字を付けます。

$ echo -e 'blob 14\0Hello, World!' | shasum 8ab686eafeb1f44702738c8b0f24f2567c36da6d

ソース：http ：//alblue.bandlem.com/2011/08/git-tip-of-week-objects.html

于 2011-08-29T01:42:14.323 に答える
37
于 2015-03-05T15:35:46.120 に答える
16

git hash-object

This is a quick way to verify your test method:

s='abc'
printf "$s" | git hash-object --stdin
printf "blob $(printf "$s" | wc -c)\0$s" | sha1sum

Output:

f2ba8f84ab5c1bce84a7b441cb1959cfc7093b7f
f2ba8f84ab5c1bce84a7b441cb1959cfc7093b7f  -

where sha1sum is in GNU Coreutils.

Then it comes down to understanding the format of each object type. We have already covered the trivial blob, here are the others:

于 2016-05-16T22:53:27.877 に答える
3

Based on Leif Gruenwoldt answer, here is a shell function substitute to git hash-object :

git-hash-object () { # substitute when the `git` command is not available
    local type=blob
    [ "$1" = "-t" ] && shift && type=$1 && shift
    # depending on eol/autocrlf settings, you may want to substitute CRLFs by LFs
    # by using `perl -pe 's/\r$//g'` instead of `cat` in the next 2 commands
    local size=$(cat $1 | wc -c | sed 's/ .*$//')
    ( echo -en "$type $size\0"; cat "$1" ) | sha1sum | sed 's/ .*$//'
}

Test:

$ echo 'Hello, World!' > test.txt
$ git hash-object test.txt
8ab686eafeb1f44702738c8b0f24f2567c36da6d
$ git-hash-object test.txt
8ab686eafeb1f44702738c8b0f24f2567c36da6d
于 2016-06-27T15:05:15.717 に答える
3

I needed this for some unit tests in Python 3 so thought I'd leave it here.

def git_blob_hash(data):
    if isinstance(data, str):
        data = data.encode()
    data = b'blob ' + str(len(data)).encode() + b'\0' + data
    h = hashlib.sha1()
    h.update(data)
    return h.hexdigest()

I stick to \n line endings everywhere but in some circumstances Git might also be changing your line endings before calculating this hash so you may need a .replace('\r\n', '\n') in there too.

于 2017-05-14T12:30:04.020 に答える