如何在github中比较/ diff特定版本的master和fork repo

Question

There are two repos on Github:

"Repo1" is a master that has regular commits (not yet forked by me) "Repo2" is a fork of Repo1 from about 2 years ago (not yet forked by me)

I want to do a DIFF between the two Repos, based on the version of code in "Repo1" that was branched by "Repo2" (approx 2 yrs ago). My objective is to then get the most recent code from "Repo1", and the now isolated changes from "Repo2", and merge these into a new "Repo3", effectively bringing the changes added to a fork 2 yrs ago, into my new fork of the most recent code of "Repo1".

One of the issues I am having is when I try to fork more than one Fork form the same root/master it doesnt seem to work, just points me back to the first fork. I am thinking I need to clone everythign locally, and do the required work there then push back to a new clean merged repo?

Any guidance much appreciated.

Answer 1

I try to fork more than one Fork form the same root/master

You don't have to fork more than one repo: fork only the repo you intent to contribute to (through PR - Pull Request). Here, fork Repo1, then clone it locally.

On your local clone, type:

git remote add /url/repo2
git fetch repo2

Then you can diff between master and repo2/master .

git diff repo2/master..master

See more at " Showing which files have changed between git branches "

git diff --name-status repo2/master..master

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The OP qtime67 adds in the comments :

as Repo1 has moved on greatly since Repo2 was forked, I wish to first see only the core changes made between the original Fork (Repo2) and the version of Repo1 at the time the fork was made.

As described in " Git diff .. ? What's the difference between having .. and no dots ", that would be using three dots:

git diff repo2/master...master
git diff master...repo2/master

A three dots diff will diff from the common ancestor ( git merge-base foo master )