René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Support `git patch-id` to compare the changes in different diffs","articleBody":"(Context: I asked about whether this feature exists in the libgit2 slack channel, and @ethomson mentioned I should create an issue for it here.)\r\n\r\nI'm looking for a way to compare two diffs to see if they modify precisely the same lines. When using git from the command line I would do this with `git patch-id`, but I don't think there is a way to determine something like a `patch-id` with libgit2.\r\n\r\n---\r\n\r\nExample of a scenario where `git patch-id` is useful on the command line:\r\n\r\n1. Start from `master` with an existing file called `foo.txt`.\r\n1. Create a branch `branchA` from master and make a commit `aaaaaaa` that modifies `foo.txt`.\r\n1. Create a branch `branchB` from master and make a commit `bbbbbbb` that modifies a different part of `foo.txt`.\r\n1. Cherry-pick commit `aaaaaaa` onto `branchB`.\r\n\r\n`git diff branchB^ branchB` and `git diff master branchA` print out the \"same\" diff (they make the same changes to the same lines), but the textual output of the commands is different, because the diff output includes the line `index something..somethingElse` at the top. (I'm not sure exactly what this line means, but I think it's related to the state of the file at the base of the diff.)\r\n\r\nTo accurately compare the two, you can pipe both diff outputs to `git patch-id` before comparing them, i.e. compare `git diff branchB^ branchB | git patch-id` and `git diff master branchA | git patch-id`. `git patch-id` effectively hashes only the changed lines in a diff, and strips out the other metadata, so it allows diffs to be compared based on whether they make the same changes to the same lines.","author":{"url":"https://github.com/not-an-aardvark","@type":"Person","name":"not-an-aardvark"},"datePublished":"2017-06-14T08:57:45.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/4270/libgit2/issues/4270"}