feat(args): add --body-file flag to load changelog body from a file

git-cliff/src/args.rs

@@ -219,9 +219,18 @@ pub struct Opt {
         long,
         env = "GIT_CLIFF_TEMPLATE",
         value_name = "TEMPLATE",
-        allow_hyphen_values = true
+        allow_hyphen_values = true,
+        conflicts_with = "body_file"
     )]
     pub body: Option<String>,
+    /// Sets the template for the changelog body from a file.
+    #[arg(
+        long,
+        env = "GIT_CLIFF_TEMPLATE_FILE",
+        value_name = "PATH",
+        value_parser = Opt::parse_dir
+    )]
+    pub body_file: Option<PathBuf>,
     /// Processes the commits starting from the latest tag.
     #[arg(short, long, help_heading = Some("FLAGS"))]
     pub latest: bool,
@@ -585,6 +594,30 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn body_file_is_parsed_as_path() -> Result<(), Box<dyn std::error::Error>> {
+        let opt = Opt::try_parse_from(["git-cliff", "--body-file", "template.tera"])?;
+        assert_eq!(Some(PathBuf::from("template.tera")), opt.body_file);
+        assert_eq!(None, opt.body);
+        Ok(())
+    }
+
+    #[test]
+    fn body_and_body_file_conflict() {
+        let result = Opt::try_parse_from([
+            "git-cliff",
+            "--body",
+            "{{ version }}",
+            "--body-file",
+            "template.tera",
+        ]);
+        assert!(result.is_err());
+        assert_eq!(
+            result.unwrap_err().kind(),
+            clap::error::ErrorKind::ArgumentConflict
+        );
+    }
+
     // Environment variables are process-global, so tests that modify them must run exclusively and
     // restore the original state after execution. For this reason, we use the `serial` macro
     // from the `serial_test` crate to guarantee exclusive execution. See: https://crates.io/crates/serial_test

git-cliff/src/lib.rs

@@ -637,6 +637,8 @@ pub fn run_with_changelog_modifier<'a>(
     }
     if let Some(body) = args.body.clone() {
         config.changelog.body = body;
+    } else if let Some(body_file) = args.body_file.clone() {
+        config.changelog.body = fs::read_to_string(&body_file)?;
     }
     if args.sort == Sort::Oldest {
         args.sort = Sort::from_str(&config.git.sort_commits, true)

website/docs/usage/args.md

@@ -47,6 +47,7 @@ git-cliff [FLAGS] [OPTIONS] [--] [RANGE]
 -o, --output [<PATH>]              Writes output to the given file [env: GIT_CLIFF_OUTPUT=]
 -t, --tag <TAG>                    Sets the tag for the latest version [env: GIT_CLIFF_TAG=]
 -b, --body <TEMPLATE>              Sets the template for the changelog body [env: GIT_CLIFF_TEMPLATE=]
+    --body-file <PATH>             Sets the template for the changelog body from a file [env: GIT_CLIFF_TEMPLATE_FILE=]
     --from-context <PATH>          Generates changelog from a JSON context [env: GIT_CLIFF_CONTEXT=]
 -s, --strip <PART>                 Strips the given parts from the changelog [possible values: header, footer, all]
     --sort <SORT>                  Sets sorting of the commits inside sections [default: oldest] [possible values: oldest, newest]

website/docs/usage/examples.md

@@ -99,6 +99,12 @@ Set/remove the changelog parts:
 git cliff --body $template --strip footer
 ```
 
+Read the body template from a file (useful for multiline templates):
+
+```bash
+git cliff --body-file template.tera
+```
+
 Skip running the commands defined in [pre](/docs/configuration/git#commit_preprocessors)/[postprocessors](/docs/configuration/changelog#postprocessors).
 
 ```bash