Reviving this thread, since I never quite got to my solution. Here's an interesting tool I found which attempts to solve this problem: https://git.sr.ht/~nhaehnle/diff-modulo-base
However it's designed more for rebases, and it doesn't seem to produce the correct (where correct === what GitHub would show) output when looking at two commits with a merge in between. - Sam On Wednesday, 22 February 2023 at 04:58:46 UTC-8 philip...@iee.email wrote: > further example courtesy of Microsoft ... " Git history simplification can > be a confusing beast. " > > https://learn.microsoft.com/en-us/azure/devops/repos/git/git-log-history-simplification?view=azure-devops > > (ignore those '>' vs '>' html errors in the git code examples ;-) > On Wednesday, February 22, 2023 at 12:23:50 PM UTC Philip Oakley wrote: > >> I haven't tried to follow that example properly yet.. >> >> However one other thing to look at is the "History Simplification" that >> includes parent re-writing that's in the rev-list-options.txt file and then >> included in a number of man pages (log, show, short-log,..). There are >> some slippery concepts in there, often context dependent! >> >> https://git-scm.com/docs/git-log#_history_simplification >> >> On Wednesday, February 22, 2023 at 5:00:51 AM UTC s...@codeapprove.com >> wrote: >> >>> Thank you both for getting back to me. The discussion in the docs about >>> flattening was really interesting! I should note that the git clone / git >>> log command pair I provided gives me almost exactly what I want, but I need >>> to combine the diffs. It seems to contain the correct changes, and the >>> speed is pretty good too. >>> >>> Let me give an example of the situation I am optimizing for. I apologize >>> in advance I am going to use GitHub terms which I know are not pure git, >>> but in the end my question is a git question. >>> >>> Say you're a developer working in a many-developer repository. Here's >>> the sequence: >>> >>> - On Day 0 you check out "main" and create "my-topic-branch". You >>> add commits A, B, C, D to that branch. >>> - Now you open a pull request on GitHub asking to merge your branch >>> "my-topic-branch" into "master". >>> - You see a collaborator has landed a change to "main" since you >>> started. So you do "git fetch origin main && git merge main" and make a >>> merge commit in your branch. >>> - Then you add three more commits E, F, G on top of that and push >>> your branch again. So you have: A, B, C, D, (merge main), E, F, G. >>> - A coworker has already looked at commits A, B, C and wants to see >>> what you've done then. So they ask GitHub to show the diff from commits >>> D >>> through G (including the merge). >>> >>> When you do this, GitHub does something which (to me, anyway) is pretty >>> magical. You are shown only the changes that you committed to your branch >>> in D, E, F, and G. Changes which you merged in, which may or may not >>> involve the files in your Pull Request, are not shown at all since they're >>> not "yours". >>> >>> Here's a public example showing a team using this pattern. This one has >>> multiple merges, so I may need to find a cleaner example but hopefully this >>> makes sense. >>> >>> - Consider this PR: >>> https://github.com/firebase/firebase-tools/pull/5478/files >>> - This is the full diff (according to GitHub) and we can see >>> exactly one added line in CHANGELOG.md >>> - Here's a merge commit: >>> >>> https://github.com/firebase/firebase-tools/pull/5478/commits/ebce28ceb799f721d36b986705c54cbcd597a27a >>> - We can see that on the base branch, "master", a line was added >>> to the *end* of the CHANGELOG.md file. There is no such addition >>> displayed in the full diff. >>> - Here's a "magic" diff where I selected three commits (before >>> merge, merge, and after merge): >>> >>> https://github.com/firebase/firebase-tools/pull/5478/files/28b8a72561b266a2086059c0d9840ab25f03d8ae..b2d89ebd67e3f8c17c4c607c630c18096303096b >>> - We can see that the changes from the merge commit are not shown >>> as additions! But they are present as context lines. >>> >>> I need to find a sequence of git commands to produce the same exact diff >>> that GitHub produces (and ideally do it very quickly even in a large >>> repository) and I just can't figure it out. >>> >>> Thanks, >>> Sam >>> >>> >>> >>> >>> On Tuesday, 21 February 2023 at 14:12:48 UTC-8 philip...@iee.email wrote: >>> >>>> This may also be an issue of the History Simplification process and / >>>> or the 'flattening' processes for history linearisation and rebases. >>>> >>>> The flattening is a known phenomena and was currently being mentioned >>>> on the Git List, so I have noted this there. >>>> [1] https://lore.kernel.org/git/a856dd16-9876-509b...@iee.email/ >>>> <https://lore.kernel.org/git/a856dd16-9876-509b-6a99-11ea0020633c@iee.email/> >>>> >>>> There is a technical discussion of flattening in the docs at >>>> https://github.com/git/git/blob/master/Documentation/howto/keep-canonical-history-correct.txt >>>> >>>> >>>> Do note the original email title "Pull is mostly evil" ;-) (whole >>>> thread at https://lore.kernel.org/git/5363bb9...@xiplink.com/ >>>> <https://lore.kernel.org/git/5363bb9f.40...@xiplink.com/>) >>>> >>>> Clarifying the " excluding merge commit changes" (or misunderstandings >>>> if you've there were some..) would be really useful. The existing devs do >>>> have the 'curse of knowledge' so often can't see the problems. >>>> On Tuesday, February 21, 2023 at 5:29:36 PM UTC Konstantin Khomoutov >>>> wrote: >>>> >>>>> On Mon, Feb 20, 2023 at 09:27:20PM -0800, 'Samuel Stern' via Git for >>>>> human beings wrote: >>>>> >>>>> > This is an *extremely* specific question which I've been trying to >>>>> get an >>>>> > answer to for quite a while now, so hopefully someone here knows the >>>>> answer. >>>>> > >>>>> > Let's say I am starting from nothing, an empty directory on a >>>>> server. I >>>>> > have: >>>>> > >>>>> > - The URL for a public git repository >>>>> > - Two endpoint SHAs (commits on the same branch) >>>>> > >>>>> > I want to get the complete diff between those commits *excluding* >>>>> merge >>>>> > commit changes, and I want to do this as fast as possible (so much >>>>> faster >>>>> > than cloning everything and diffing). >>>>> > >>>>> > I am able to get almost there with the following sequence: >>>>> > >>>>> > # Fast clone >>>>> > git clone --verbose --no-checkout --filter=blob:limit=250k >>>>> --single-branch >>>>> > --branch=${branch} --depth=${depth} $REPO_URL >>>>> > >>>>> > # Get a series of patches >>>>> > git log --no-merges --first-parent --patch ${base.sha}..${head.sha} >>>>> > >>>>> > However I need to get a *single* patch that represents all the >>>>> changes >>>>> > combined, not a series of patches from the log. >>>>> >>>>> Isn't mere >>>>> >>>>> git diff ${head.sha} ${base.sha} >>>>> >>>>> is what you're looking for? >>>>> >>>>> Otherwise, I'm with Philipp in that your statements (rephrased) >>>>> >>>>> - I want to get a single combined change ("patch") describing the >>>>> literal >>>>> set of changes between such and such commits. >>>>> >>>>> - I want changes brought in by merge commits excluded. >>>>> >>>>> Contradict each other: I could in principle envision some algorithm >>>>> which >>>>> would try to incrementally produce a diff as in walks a chain of >>>>> commits and >>>>> tries to ignore the changes introduced by merge commits located in >>>>> that chain, >>>>> but leaving aside the fact such an algotithm would be very brittle for >>>>> any >>>>> real-world cases, I simply see no use for it - even a theoretical one. >>>>> >>>>> >>>>> You might got trapped by the fact you have found `git log` first in >>>>> your >>>>> search, and this command traverses all individual commits in the >>>>> subgraph it's >>>>> told to traverse - including "sidelines" brought in by merge commits. >>>>> Instead, plain old `git diff` does not traverse anything: it takes two >>>>> states >>>>> of the project and compares them. >>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "Git for human beings" group. 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