Update main.rs to use new attachment iface

src/main.rs

@@ -1,3 +1,5 @@
+use std::fs;
+
 use gt_tool::cli::Args;
 use gt_tool::structs::release::{CreateReleaseOption, Release};
 
@@ -78,14 +80,26 @@ async fn main() -> Result<(), gt_tool::Error> {
                 gt_tool::api::release::list_releases(&client, &args.gitea_url, &args.repo).await?;
 
             if let Some(release) = match_release_by_tag(&tag_name, release_candidates) {
-                gt_tool::api::release_attachment::create_release_attachment(
+                for file in &files {
+                    match fs::exists(file) {
+                        Ok(true) => continue,
+                        Ok(false) => return Err(gt_tool::Error::NoSuchFile),
+                        Err(e) => {
+                            eprintln!("Uh oh! The file-exists check couldn't be done: {e}");
+                            panic!("TODO: Deal with scenario where the file's existence cannot be checked (e.g.: no permission)");
+                        },
+                    }
+                }
+                for file in files {
+                    let _attach_desc = gt_tool::api::release_attachment::create_release_attachment(
                         &client,
                         &args.gitea_url,
                         &args.repo,
                         release.id,
-                    files,
+                        file,
                     )
                     .await?;
+                }
             } else {
                 println!("ERR: Couldn't find a release matching the tag \"{tag_name}\".");
                 return Err(gt_tool::Error::NoSuchRelease);