How to compare a file on disk with a file from a different branch which does not exist on disk

I want to perform a comparison operation between a file which exists on disk and a file which no longer exists because I moved it.

Here's the situation.

• I had a file which existed in a folder. Let's call it ./src/A.txt.
• I moved A.txt to a new folder. It's now called ./doc/A.txt.
• I edited ./doc/A.txt.

I now want to compare ./doc/A.txt with the state of ./src/A.txt which exists on the branch origin/main. Of course, this file does not actually exist in the current working directory.

I think one possible way to do this might be to do the following:

• git checkout origin/main ./src/A.txt
• git diff ./src/A.txt ./doc/A.txt

(Edit: Nope - this doesn't work. Use diff ./src/A.txt ./doc/A.txt instead.)

Is there a way to do it "directly"?

Maybe something like

git diff ./src/A.txt@origin/main ./doc/A.txt

You can get what you want with:

git show origin/main:./src/A.txt | diff - doc/A.txt

or

git diff origin/main:./src/A.txt doc/A.txt