Merge #4812

4812: Allow `MEILI_NO_VERGEN` env var to skip vergen r=irevoire a=dureuill

- vergen checks the state of the `.git` directory to embed commit information into the `meilisearch` binary and the `cargo xtask bench` invocations.
- This check unfortunately results in too many recompilation of the `meilisearch` binary.
- This PR allows skipping vergen when the `MEILI_NO_VERGEN` variable is present in the environment

Co-authored-by: Louis Dureuil <louis@meilisearch.com>

CONTRIBUTING.md

@@ -62,6 +62,10 @@ We recommend using the standard `$HOME/.cache/lindera` directory:
 export LINDERA_CACHE=$HOME/.cache/lindera
 ```
 
+Furthermore, you can improve incremental compilation by setting the `MEILI_NO_VERGEN` environment variable.
+Setting this variable will prevent the Meilisearch binary from being rebuilt each time the directory that hosts the Meilisearch repository changes.
+Do not enable this environment variable for production builds (as it will break the `version` route, among other things).
+
 #### Snapshot-based tests
 
 We are using [insta](https://insta.rs) to perform snapshot-based testing.

build-info/build.rs

@@ -5,6 +5,13 @@ fn main() {
 }
 
 fn emit_git_variables() -> anyhow::Result<()> {
+    println!("cargo::rerun-if-env-changed=MEILI_NO_VERGEN");
+
+    let has_vergen =
+        !matches!(std::env::var_os("MEILI_NO_VERGEN"), Some(x) if x != "false" && x != "0");
+
+    anyhow::ensure!(has_vergen, "disabled via `MEILI_NO_VERGEN`");
+
     // Note: any code that needs VERGEN_ environment variables should take care to define them manually in the Dockerfile and pass them
     // in the corresponding GitHub workflow (publish_docker.yml).
     // This is due to the Dockerfile building the binary outside of the git directory.