Use pre Rust 1.81 compatible file-exists test

The function `std::fs::exists(...)` was stabilized in Rust 1.81, which
means it can't be used in the Debian Bookworm build. This patch swaps to
a compatible implementation leaning on the std::path::Path struct.

I'm both "upstreaming" a Debian-specific patch I had to make for the
package, and fixing the additional usage now in `main.rs`. There doesn't
seem to be any compelling reason to avoid using this function, so I
figure I should merge it into the base release.

README.md

@@ -51,14 +51,3 @@ One of these, defaults to `help`:
 | upload-release | Uploads one-or-more files to an existing release, identified by it's tag name. |
 | help | prints the help text (the usage summary above). |
 
-## Unit Testing
-
-The unit test~~s~~ require a Gitea server to execute against. This information is supplied by environment variables rather than on the command line, but it is otherwise exactly the same usage.
-
-| Variable | Description |
-|-|-|
-| TEST_GITEA_SERVER | Server URL, match `-u`, `--url` |
-| TEST_GITEA_REPO | Owner + repo name, match `-u` `--repo` |
-| TEST_GITEA_KEY | API key, match `RELEASE_KEY_GITEA`. The use of a new variable for the API token is to help avoid accidentally touching a production environment during test execution. |
-| TEST_GITEA_RELEASE_TAG | Git tag used to identify the Release. Same as `upload-release`'s positional argument `<TAG_NAME>`. |
-

src/api/release.rs

@@ -1,6 +1,6 @@
 
 use crate::{
-    ApiError, Result,
+    Result,
     structs::{
         release::{CreateReleaseOption, Release},
     },

src/api/release_attachment.rs

@@ -1,4 +1,4 @@
-use std::fs;
+use std::{fs, path};
 
 use crate::structs::Attachment;
 
@@ -16,7 +16,8 @@ pub async fn create_release_attachment(
 ) -> crate::Result<Attachment> {
     let request_url = format!("{gitea_url}/api/v1/repos/{repo}/releases/{release_id}/assets");
 
-    match fs::exists(&file) {
+    let path = path::Path::new(&file);
+    match path.try_exists() {
         Ok(true) => (),
         Ok(false) => return Err(crate::Error::NoSuchFile),
         Err(e) => {

src/main.rs

@@ -1,4 +1,5 @@
-use std::fs;
+
+use std::path;
 
 use gt_tool::cli::Args;
 use gt_tool::structs::release::{CreateReleaseOption, Release};
@@ -81,7 +82,8 @@ async fn main() -> Result<(), gt_tool::Error> {
 
             if let Some(release) = match_release_by_tag(&tag_name, release_candidates) {
                 for file in &files {
-                    match fs::exists(file) {
+                    let path = path::Path::new(&file);
+                    match path.try_exists() {
                         Ok(true) => continue,
                         Ok(false) => return Err(gt_tool::Error::NoSuchFile),
                         Err(e) => {