git-diff-index(1)

Each diff block contains the changes of one file, and starts with line: ... index, which represents the unchanged lines percentage of the file.

DESCRIPTION. Compare the content and mode of the blobs found in a tree object with the corresponding tracked files in the working tree, or with the ...

将树对象中发现的blob 的内容和模式与工作树中的相应跟踪文件或索引中的相应路径进行比较。 如果存在<路径> 参数，则只比较与这些模式匹配的路径。

'git diff-index' [-m] [--cached] [--merge-base] [<common-diff-options>] <tree-ish> [<path>...] files are compared. The id of a tree object to diff against. Do ...

git diff. 比對的是現在的工作區跟index的差異 ; git diff --cached []. 比對index與指定commit的差異 ; git diff [options]. 指定的兩個commit的差異 ; git diff [options].

Compares the content and mode of the blobs found via a tree object with the content of the current index and, optionally ignoring the stat state of the file ...

DESCRIPTION Compares the content and mode of the blobs found in a tree object with the corresponding tracked files in the working tree, or with the ...

f2e4113 and d4b9bfc are file-indexes. With git show f2e4113 you see the file before the commit and git show d4b9bfc shows the file after the ...

git diff-index is a diff against the index or working tree: Compares the content and mode of the blobs found in a tree object with the corresponding tracked ...

I don't know of a diff tool that accepts multiple pairs of files to compare. Even diff only accepts a single pair of files, or a directory and a list of files.