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Comment by Peaker | Hacker News Reader

When you have that many conflicts, it's often due to massive renames, or just code moves.

If you use git-mediate[1], you can re-apply those massive changes on the conflicted state, run git-mediate - and the conflicts get resolved.

For example: if you have 300 conflicts due to some massive rename, you can type in:

  git-search-replace.py[2] -f oldGlobalName///newGlobalName
  git-mediate -d
  Succcessfully resolved 377 conflicts and failed resolving 1 conflict.
  <1 remaining conflict shown as 2 diffs here representing the 2 changes>

[1] https://medium.com/@yairchu/how-git-mediate-made-me-stop-fea...

[2] https://github.com/da-x/git-search-replace

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Also git rerere

When maintaining multiple release lines and moving fixes between them:

Don't use a bad branching model. Things like "merging upwards" (=committing fixes to the oldest branch requiring the fix, then merging the oldest branch into the next older branch etc.), which seems to be somewhat popular, just don't scale, don't work very well, and produce near-unreadable histories. They also incentivise developing on maintenance branches (ick).

Instead, don't do merges between branches. Everything goes into master/dev, except stuff that really doesn't need to go there (e.g. a fix that only affects a specific branch(es)). Then cherry pick them into the maintenance branches.

Cherry picking hotfixes into maint branches is cool until you have stuff like diverging APIs or refactored modules between branches. I don't know of a better solution; it kind of requires understanding in detail what the fix does and how it does it, then knowing if that's directly applicable to every release which needs to be patched.

Use namespaces to separate API versions?

POST /v4/whatever

POST /v3/whatever

We version each of our individual resources. so a /v1/user might have many /v3/post . Seems to work for us as a smaller engineering team.

A better approach would be to alias /v3/user to /v1/user until there is a breaking change needed in the v3 code tier.

On a rapidly developing API, that would be way too much churn on our front end. For an externally facing API, I completely agree.

Yes, although this applies to all forms of porting changesets or patches between branches or releases.

I don't understand the hate for merging up. I've worked with the 'cherry-pick into release branches' model, and also with an automated merge-upwards model, and I found the automerge to be WAY easier to deal with. If you make sure your automerge is integrated into your build system, so a failing automerge is a red build that sends emails to the responsible engineers, I found that doing it this way removed a ton of the work that was necessary for cherry-picking. I can understand not liking the slightly-messier history you get, but IMO it was vastly better. Do you have other problems with it, or just 'unreadable' histories and work happening on release branches? Seems like a good trade to me.

As the branches diverge, merges take more and more time to do (up to a couple hours, at which point we abandoned the model)... they won't be done automatically. Since merges are basically context-free it's hard to determine the "logic" of changed lines. Since merges always contain a bunch of changes, all have to be resolved before they can be tested, and tracing failures back to specific conflict resolutions takes extra time. Reviewing a merge is seriously difficult. Mismerges are also far more likely to go unnoticed in a large merge compared to a smaller cherry pick. With cherry picking you are only considering one change, and you know which one. You only have to resolve that one change, and can then test, if you feel that's necessary, or move on to the next change.

Also; https://news.ycombinator.com/item?id=14413681

I also observed that getting rid of merging upwards moved the focus of development back to the actual development version (=master), where it belongs.

I just looked at git-mediate and I'm very confused. It appears that all it does is remove the conflict markers from the file after you've already manually fixed the conflict. Except you need to do more work than normal, because you need to apply one of the changes not only to the other branch's version but also to the base. What am I missing here, why would I actually want to use git-mediate when I'm already doing all the work of resolving the conflicts anyway?

It looks like git-mediate does one more important thing; it checks that the conflict is actually solved. In my experience it's very easy to miss something when manually resolving a conflict and often the choices the merge tools give you are not the ones you want.

IntelliJ IDEA default merger knows when all conflicts in a file are handled and shows you a handy notification on top "Save changes and finish merging".

TFS's conflict resolver also does this

Well, all it checks is that you modified the base case to look like one of the two other cases. That doesn't actually tell you if you resolved the conflict though, just that you copied one of the cases over the base case.

True, but if you follow a simple mechanical guideline: Apply the change 2 other versions (preferably the base one last) - then your conflict resolutions are going to be correct.

From experience with many developers using this method, conflict resolution errors went down to virtually zero, and conflict resolution time has improved by 5x-10x.

There's a much simpler mechanical guideline that works without git-mediate: Apply the change to the other version. git-mediate requires you to apply the change twice, but normal conflict resolution only requires you to apply it once.

Except you don't really know if you actually applied the full change to the other version. That's what applying it to the base is all about.

You often take the apparent diff, apply it to the other version, and then git-mediate tells you "oops, you forgot to also apply this change". And this is one of the big sources of bugs that stem from conflict resolutions.

Another nice thing about git-mediate is that it lets you safely do the conflict resolution automatically, e.g: via applying a big rename as I showed in the example, and seeing how many conflicts disappear. This is much safer than manually resolving.

Applying the change to the base doesn't prove that you applied the change to the other version. It only proves that you did the trivial thing of copying one version over the base. That's kinda the whole point of my complaint here, git-mediate is literally just having you do busy-work as a way of saying "I think I've applied this change", and that busy-work has literally no redeeming value because it's simply thrown away by git-mediate. Since git-mediate can't actually tell if you applied the change to the other version correctly, you're getting no real benefit compared to just deleting the conflict markers yourself.

The only scenario in which i can see git-mediate working is if you don't actually resolve conflicts at all but instead just do a project-wide search&replace, but that's only going to handle really trivial conflicts, and even then if you're not actually looking at the conflict you run the risk of having the search & replace not actually do what it's supposed to do (e.g. catching something it shouldn't).

> Since git-mediate can't actually tell if you applied the change to the other version correctly, you're getting no real benefit compared to just deleting the conflict markers yourself

This is patently and empirically false:

1) See the automated rename example. How do you gain the same safety and ease of resolution without git mediate? This is, unlike you say, an incredibly common scenario. After all, conflicts are usually due to very wide, mechanical changes. The exact kinds of changes that are easy to re-apply project-wide. It is true for not only renames, but also whitespace fixes which are infamous for causing conflicts and thus inserting bugs, and due to that are not allowed in many collaborative projects!

2) Instead of having to tediously compare the 3 versions to make sure you haven't missed any change when resolving (a very common error!) you now have to follow a simple guideline: Apply the same change to 2 versions.

This guideline is simple enough to virtually never fuck it up, unlike traditional conflict resolution which is incredibly error-prone. Your complaint that git mediate does not validate you followed this one guideline is moot, since this guideline is so easy to not fuck up - compared to the rest of the resolution process.

If you follow this guideline - git-mediate has tremendous value. It makes sure you did not forget any part of the change done by either side - and streamlines every other part of the conflict resolution process:

A) Takes my favorite editor directly to the conflict line

B) Shows me 2 diffs instead of 3 walls of text

C) Lets me choose the simpler diff to apply to the other sides, making a very minimal text change in my editor.

D) Validates that the change I applied was the last one (or decreases the size of the diff otherwise)

E) Does the "git add" for me, and takes me directly to the next conflict

This has been used by dozens of people, who can all testify that it:

A) Made conflict resolution easy and convenient

B) Reduced the error rate to zero (I don't remember the lasts bug inserted in a merge conflict)

C) Sped the process up by an order of magnitude

> See the automated rename example. How do you gain the same safety and ease of resolution without git mediate? This is, unlike you say, an incredibly common scenario.

Is it? I'm not sure if I've ever had a conflict that would be resolved by a global find & replace. Globally renaming symbols isn't really all that common. In my experience conflicts are not "usually due to very wide, mechanical changes", they're due to two people modifying the same file at the same time.

> It is true for not only renames, but also whitespace fixes which are infamous for causing conflicts …

Most projects don't go doing whitespace fixes over and over again. In projects that do any sort of project-wide whitespace fixes, that sort of thing is usually done once, at which point the whitespace rules are enforced on new commits. So yes, global whitespace changes can cause commits, but they're rather rare.

> Instead of having to tediously compare the 3 versions to make sure you haven't missed any change when resolving (a very common error!) you now have to follow a simple guideline: Apply the same change to 2 versions.

> This guideline is simple enough to virtually never fuck it up

You know what's even simpler? "Apply the same change to 1 version". Saying "Fix the conflict, and then do extra busy-work on top of it" is not even remotely "simpler". It's literally twice the amount of work.

The only thing git-mediate appears to do is tell you if a project-wide find&replace was sufficient to resolve your conflict (and that's assuming the project-wide find&replace is even safe to do, as I mentioned in my previous comment). If you're not doing project-wide find&replaces, then git-mediate just makes your job harder.

From reading your "process" it appears that all you really need is a good merge tool, because most of what you describe as advantageous is what you'd get anyway when using any sort of reasonable tool (e.g. jumping between conflicts, showing correct diffs, making it easy to copy lines from one diff into another, making it easy to mark the hunk as resolved).

> In my experience conflicts are not "usually due to very wide, mechanical changes", they're due to two people modifying the same file at the same time.

Then it is likely a reversal of cause & effect. People are more reluctant to make wide sweeping changes such as renames because they're worried about the ensuing conflicts.

> Most projects don't go doing whitespace fixes over and over again

Again, for similar reasons. Projects limp around with broken indentation (tabs/spaces), trailing whitespaces, dos newlines, etc - because fixing whitespace is against policy. Why? Conflicts.

> You know what's even simpler? "Apply the same change to 1 version".

It sounds simpler, but not fucking it up is not simple at all, as evidenced by conflicts being a constant source of bugs.

When you look at the 3 versions, and "apply the diff to 1 version" you actually think you apply the diff to 1 version. You're applying the perceived diff to 1 version, which often differs from the actual diff as it may include subtle differences that aren't easily visible. This is detected by git-mediate the double-accounting of applying the perceived diff to both - validating that the perceived diff equals the actual diff.

Without git-mediate? At best you bring up build errors. At worst, revive old bugs that were subtly fixed in the diff you think you applied.

> then git-mediate just makes your job harder.

You're talking out of your ass here. Me and 20 other people have been using git-mediate and it's been a huge game changer for conflict resolution. Every single user I've talked to claims huge productivity/reliability benefits from using it.

> all you really need is a good merge tool

I've used "good" merge tools a lot. They're incredibly inferior to my favorite text editor:

* Text editing within them is tedious and terrible

* Their supported actions of copying whole lines from one version to the other are useless 90% of the time.

Let me ask you this:

What percentage of the big conflicts you resolve with a "good merge tool" - build & run correctly on the first run after resolution?

For git-mediate, that is easily >99%.

> People are more reluctant to make wide sweeping changes such as renames because they're worried about the ensuing conflicts.

I disagree. People generally don't do project-wide find&replaces because it's just not all that common to want to rename a global symbol.

> Projects limp around with broken indentation (tabs/spaces), trailing whitespaces, dos newlines, etc - because fixing whitespace is against policy. Why? Conflicts.

You seem to have completely missed the point of my comment. I'm not saying projects limp along with bad whitespace. I'm saying projects that decide upon whitespace rules typically do a single global fixup and then simply enforce whitespace rules on all new commits. That means you only ever have one conflict set due to applying whitespace policy, rather than doing it over and over again as you suggested.

> You're applying the perceived diff to 1 version, which often differs from the actual diff as it may include subtle differences that aren't easily visible.

Then you're using really shitty merge software. Any halfway-decent merge tool will highlight all the differences for you.

> Without git-mediate? At best you bring up build errors. At worst, revive old bugs that were subtly fixed in the diff you think you applied.

And this is just FUD.

It's simple. Just stop using Notepad.exe to handle your merge conflicts and use an actual merge tool. It's pretty hard to miss a change when the tool highlights all the changes for you.

> You're talking out of your ass here.

And you're being uncivil. I'm done with this conversation.

That's why I showed an example of a rename. You write "manually fixed the conflict", where do you see that in the rename example?

You just re-apply either side of the changes in the conflict (Base->A, or Base->B) and the conflict is then detected as resolved. Reapplying (e.g: via automated rename) is much easier than what people typically mean by "manually resolving the conflict".

Also, as a pretty big productivity boost, it prints the conflicts in a way that lets many editors (sublime, emacs, etc) directly jump to conflicts, do the "git add" for you, etc. This converts your everyday editor into a powerful conflict resolution tool. Using the editing capabilities in most merge tools is tedious.

or worse, formatting changes

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