feature: make it possible to override generate dirs via env (#1658)

build.rs

@@ -38,11 +38,12 @@ fn btm_generate() -> io::Result<()> {
 
     match env::var_os(ENV_KEY) {
         Some(var) if !var.is_empty() => {
-            const COMPLETION_DIR: &str = "./target/tmp/bottom/completion/";
-            const MANPAGE_DIR: &str = "./target/tmp/bottom/manpage/";
+            let completion_dir =
+                option_env!("COMPLETION_DIR").unwrap_or("./target/tmp/bottom/completion/");
+            let manpage_dir = option_env!("MANPAGE_DIR").unwrap_or("./target/tmp/bottom/manpage/");
 
-            let completion_out_dir = PathBuf::from(COMPLETION_DIR);
-            let manpage_out_dir = PathBuf::from(MANPAGE_DIR);
+            let completion_out_dir = PathBuf::from(completion_dir);
+            let manpage_out_dir = PathBuf::from(manpage_dir);
 
             create_dir(&completion_out_dir)?;
             create_dir(&manpage_out_dir)?;

docs/content/contribution/packaging-and-distribution.md

@@ -54,6 +54,9 @@ This will automatically generate completion and manpage files in `target/tmp/bot
 files, modify/delete either these files or set `BTM_GENERATE` to some other non-empty value to retrigger the build
 script.
 
+You may override the default diretories used to generate both completion and manpage files by specifying the
+`COMPLETION_DIR` and `MANPAGE_DIR` environment variables respectively.
+
 For more information, you may want to look at either the [`build.rs`](https://github.com/ClementTsang/bottom/blob/main/build.rs)
 file or the [binary build CI workflow](https://github.com/ClementTsang/bottom/blob/main/.github/workflows/build_releases.yml).