[llvm] Change release branch creation process to bump version to N.1.0. (PR #75743)

[James Y Knight via llvm-commits]

https://github.com/jyknight created https://github.com/llvm/llvm-project/pull/75743

This will help distinguish release branch builds from development branch builds, and is similar to GCC's version numbering policy.

Thus, the branch `releases/18.x` will start out numbered 18.1.0, instead of 18.0.0.

Unchanged are other versioning policies:
- mainline will be numbered 18.0.0, 19.0.0, ...
- typical releaes branch releases will increment micro version, e.g. 18.1.1, 18.1.2, ....
- If an ABI break is required on the release branch, the minor version will be incremented, e.g. to 18.2.0.

See the Discourse RFC:
https://discourse.llvm.org/t/rfc-name-the-first-release-from-a-branch-n-1-0-instead-of-n-0-0/75384

>From 87e0b4f1fb93b920826367e729164e487dfa55cf Mon Sep 17 00:00:00 2001
From: James Y Knight <jyknight at google.com>
Date: Sun, 17 Dec 2023 12:06:04 -0500
Subject: [PATCH] Change release branch creation process to bump version to
 N.1.0.

This will help distinguish release branch builds from development
branch builds, and is similar to GCC's version numbering policy.

Thus, the branch `releases/18.x` will start out numbered 18.1.0,
instead of 18.0.0.

Unchanged are other versioning policies:
- mainline will be numbered 18.0.0, 19.0.0, ...
- typical releaes branch releases will increment micro version,
  e.g. 18.1.1, 18.1.2, ....
- If an ABI break is required on the release branch, the minor version
  will be incremented, e.g. to 18.2.0.

See the Discourse RFC:
https://discourse.llvm.org/t/rfc-name-the-first-release-from-a-branch-n-1-0-instead-of-n-0-0/75384
---
 llvm/docs/HowToReleaseLLVM.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/docs/HowToReleaseLLVM.rst b/llvm/docs/HowToReleaseLLVM.rst
index 15397c593d4977..d6b5bca28f5761 100644
--- a/llvm/docs/HowToReleaseLLVM.rst
+++ b/llvm/docs/HowToReleaseLLVM.rst
@@ -123,6 +123,9 @@ Branch the Git trunk using the following procedure:
    version bump.  The branch's name is release/X.x where ``X`` is the major version
    number and ``x`` is just the letter ``x``.
 
+#. On the newly-created release branch, immediately bump the version
+   to X.1.0git (where ``X`` is the major version of the branch.)
+
 #. All tags and branches need to be created in both the llvm/llvm-project and
    llvm/llvm-test-suite repos.