Updating Postgres

Minor Versions

When upgrading to a new minor version of Postgres, please follow these steps:

Example: 15.4 is the new minor version to upgrade to from 15.3.

Clone the Neon Postgres repository if you have not done so already.
```
git clone git@github.com:neondatabase/postgres.git
```

Add the Postgres upstream remote.

git remote add upstream https://git.postgresql.org/git/postgresql.git

Create a new branch based on the stable branch you are updating.
```
git checkout -b my-branch-15 REL_15_STABLE_neon
```
Find the upstream release tags you're looking for. They are of the form REL_X_Y.
Merge the upstream tag into the branch you created on the tag and resolve any conflicts.
```
git fetch upstream REL_15_4
git merge REL_15_4
```
In the commit message of the merge commit, mention if there were any non-trivial conflicts or other issues.
Run the Postgres test suite to make sure our commits have not affected Postgres in a negative way.
```
make check
# OR
meson test -C builddir
```
Push your branch to the Neon Postgres repository.
```
git push origin my-branch-15
```
Clone the Neon repository if you have not done so already.
```
git clone git@github.com:neondatabase/neon.git
```
Create a new branch.
Change the revisions.json file to point at the HEAD of your Postgres branch.

Update the Git submodule.

git submodule set-branch --branch my-branch-15 vendor/postgres-v15
git submodule update --remote vendor/postgres-v15

Run the Neon test suite to make sure that Neon is still good to go on this minor Postgres release.
```
./scripts/poetry -k pg15
```
Commit your changes.
Create a pull request, and wait for CI to go green.
Push the Postgres branches with the merge commits into the Neon Postgres repository.
```
git push origin my-branch-15:REL_15_STABLE_neon
```

Update your Neon PR to point at the branches.

git submodule set-branch --branch REL_15_STABLE_neon vendor/postgres-v15
git commit --amend --no-edit
git push --force origin