git - 是否可以在 Git 目录之外创建 Git 哈希对象？

Question

我正在尝试获取 2 个字符串之间的 git diff。以下命令有效:

git diff $(echo "my first string" | git hash-object -w --stdin) $(echo "my second string" | git hash-object -w --stdin)  --word-diff

但是，如果不在 Git 目录中执行，它将失败。

我认为这部分命令失败了:

echo "my first string" | git hash-object -w --stdin

有什么办法可以在 Git 目录外执行吗？

Answer 1

I believe this portion of the command is failing:

echo "my first string" | git hash-object -w --stdin

Is there any way around this so that it can be executed outside a git directory?

您遇到的问题是因为您传递给 git hash-object 命令的 -w 选项。该选项需要一个现有的存储库，因为它有 writing the object into the git database 的副作用.

证明:

$ echo "my first string" | git hash-object -w --stdin
fatal: Not a git repository (or any parent up to mount point /home)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).

$ echo "my first string" | git hash-object --stdin
3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165

但是，由于您的最终目标是获取两个给定字符串之间的 git diff，如果您想在 git hash-object 的帮助下完成此操作，则必须拥有一个 git 存储库¹。为此，您可以生成一个临时的空存储库:

$ tmpgitrepo="$(mktemp -d)"

$ git init "$tmpgitrepo"
Initialized empty Git repository in /tmp/tmp.MqBqDI1ytM/.git/

$ (export GIT_DIR="$tmpgitrepo"/.git; git diff $(echo "my first string" | git hash-object -w --stdin) $(echo "my second string" | git hash-object -w --stdin)  --word-diff)
diff --git a/3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165 b/2ab8560d75d92363c8cb128fb70b615129c63371
index 3616fde..2ab8560 100644
--- a/3616fdee3ac48e5db02fbf9d5e1c2941cfa3e165
+++ b/2ab8560d75d92363c8cb128fb70b615129c63371
@@ -1 +1 @@
my [-first-]{+second+} string

$ rm -rf "$tmpgitrepo"

这种方式可以打包成一个bash函数:

git-diff-strings()
(
    local tmpgitrepo="$(mktemp -d)"
    trap "rm -rf $tmpgitrepo" EXIT
    git init "$tmpgitrepo" &> /dev/null
    export GIT_DIR="$tmpgitrepo"/.git
    local s1="$1"
    local s2="$2"
    shift 2
    git diff $(git hash-object -w --stdin <<< "$s1") $(git hash-object -w --stdin <<< "$s2") "$@"
)

用法:

git-diff-strings <string1> <string2> [git-diff-options]

示例:

git-diff-strings "first string" "second string" --word-diff

---

¹ 请注意，您可以通过创建 2 个包含这些字符串的临时文件来git diff 两个字符串，在这种情况下您不需要 git 存储库。