Automatically create release tags via GitHub actions

Release tags are now created automatically when including an indicator
(see updated documentation) in the commit message.

For now: keep automated release tagging in dry-run mode (we should first
make sure this actually works on this repository before enabling it in
production).

.github/workflows/release-create-tag.yaml

@@ -0,0 +1,28 @@
+name: Create release tag
+on:
+  push:
+    branches: [ develop ]
+    paths:
+      - 'src/config.inc'
+
+jobs:
+  create-tag:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: '0'
+    - name: Get version
+      run: |
+        v=$(grep ^CBMC_VERSION src/config.inc | perl -p -e 's/^CBMC_VERSION\s*=\s*//')
+        echo "CBMC_VERSION=$v" >> $GITHUB_ENV
+    - name: Set new tag
+      uses: anothrNick/github-tag-action@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        RELEASE_BRANCHES: develop
+        CUSTOM_TAG: cbmc-${{ env.CBMC_VERSION }}
+        VERBOSE: false
+        DRY_RUN: true

doc/ADR/release_process.md

@@ -10,23 +10,18 @@
 The current process we follow through to make a new release is the following:
 
 1. At the point in time we want to make the release, we make a change to
-   two files: `src/config.inc`, wherein we update the configuration variable
-   `CBMC_VERSION`, and `src/libcprover-rust/Cargo.toml`, wherein we update
+   three files: `src/config.inc`, wherein we update the configuration variable
+   `CBMC_VERSION`, src/libcprover-rust/Cargo.toml`, wherein we update
    the `version` variable to be the same as `CBMC_VERSION` (e.g. set both
-   to `5.80.0`).
+   to `5.80.0`), and CHANGELOG.
 
-   This is important as it informs the various tools of the current version
-   of CBMC.
+   This is important as it informs the various tools of the current version of
+   CBMC. These changes need to be pushed as a PR. Once that PR is merged into
+   `develop`, a Git tag of the form `cbmc-<version>` (where `<version>` is the
+   value of `CBMC_VERSION`) is automatically created. This tag then triggers
+   further automatic steps, see below.
 
-   (This needs to be pushed as a PR, and after it gets merged we move on to:)
-
-2. Then we make a `git tag` out of that commit, and push it to github. The
-   tag needs to be of the form `cbmc-<version>` with version being a version
-   number of the form of `x.y.z`, with `x` denoting the major version, `y`
-   denoting the minor version, and `z` identifying the patch version (useful
-   for a hotfix or patch.)
-
-3. Pushing the Rust crate, which is documented [here](https://doc.rust-lang.org/cargo/commands/cargo-publish.html)
+2. Pushing the Rust crate, which is documented [here](https://doc.rust-lang.org/cargo/commands/cargo-publish.html)
    but effectively entails logging in with an API token generated from
    https://crates.io with `cargo login`, and then issuing `cargo publish`.