[happimess]

> Conceptually continuous integration is generally integrating 2+ different lineages of code together

> In practice, CI [often means] "automated test server"

Could you say more? I use "CI" to refer to the automated processes that run tests and (maybe) deploy code as it is merged to some blessed branch. It's what continually integrates the new code into the existing code. What am I missing?

[nijave]

If there's 1 developer working on 1 branch at a time: main is at commit A, you branch add B and C, you merge now main is at A, B, C. Your "integration" was just moving the code forward and if you ran tests on A, B, C commits and it passed, the tests would still pass on main.

Now say there's 2 developers that branch off A. Dev 1 removed dead code coolUtil and with it deleted module coolLib and commits B1. Tests pass, code works. Dev 2 adds new coolUtil2 in commit B2. Tests pass, code works. Now they both merge their changes back to branch A so it's A, B1, B2 or A, B2, B1 or A, B3 (merge of B1/2). Anyway, you try to run the code and it fails. Everything merged clean but Dev 1 removed the lib Dev 2 depends on. They didn't create any file level conflicts because they edited different things so the merging went fine however now the code is broken.

The real integration part comes from reconciling different (potentially conflicting) changes and making sure the end result still works. The server is doing the integration automatically and verifying it automatically

You could skip the server and merge everything on your machine and run the tests on your machine and achieve the same result. Still CI, no server, no automation

Hopefully that makes sense, if not I think the Wikipedia page "Practices" section does a decent job separating the pieces https://en.wikipedia.org/wiki/Continuous_integration