[features #189] simple UTC-offset support for git-features

Author: Byron

Cargo.lock

@@ -251,7 +251,7 @@ Provide a CLI to for the most basic user journey:
 [fossil-scm]: https://www.fossil-scm.org
 
 
-## Shortcomings
+## Shortcomings & Limitations
 
 * **fetches using protocol V1 and stateful connections, i.e. ssh, git, file, may hang**
   * This can be fixed by making response parsing.
@@ -277,6 +277,7 @@ Provide a CLI to for the most basic user journey:
 * **git-url** _might_ be more restrictive than what git allows as for the most part, it uses a browser grade URL parser.
   * Thus far there is no proof for this, and as _potential remedy_ we could certainly re-implement exactly what git does
     to handle its URLs.
+* **local time** is currently impeded by [this issue](https://github.com/time-rs/time/issues/293#issuecomment-909158529) but it's planned to resolve it eventually.
 
 ## Credits
 

README.md

@@ -129,6 +129,8 @@ All feature toggles are additive.
 * **cache-efficiency-debug**
     * Caches implement this by default, which costs nothing unless this feature is enabled
     * Count cache hits and misses and print that debug information on drop
+* **time**
+    * Make the `time` module available with access to the local time as configured by the system.
 
 ### git-packetline
 

cargo-features.md

@@ -17,7 +17,6 @@ progress = ["prodash"]
 parallel = ["crossbeam-utils", "crossbeam-channel", "num_cpus", "jwalk"]
 fast-sha1 = ["sha-1"]
 io-pipe = ["bytes"]
-time = ["libc"]
 crc32 = ["crc32fast"]
 zlib = ["flate2", "flate2/rust_backend", "quick-error"]
 zlib-ng-compat = ["flate2/zlib-ng-compat"]
@@ -76,7 +75,7 @@ flate2 = { version = "1.0.17", optional = true, default-features = false }
 quick-error = { version = "2.0.0", optional = true }
 
 # time module
-libc = { version = "0.2.101", optional = true }
+time = { version = "0.3.2", optional = true, default-features = false, features = ["local-offset"] }
 
 [package.metadata.docs.rs]
 all-features = true

git-features/Cargo.toml

@@ -1,7 +1,33 @@
-pub struct Local {
-    seconds_since_epoch: i64,
-    tz_offset_in_seconds: i64,
-}
-pub fn local_since_epoch() -> Local {
-    todo!("implement localtime")
+///
+pub mod tz {
+    mod error {
+        use std::fmt;
+
+        /// The error returned by [`offset()`]
+        #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+        pub struct Error;
+
+        impl fmt::Display for Error {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                f.write_str("The system's UTC offset could not be determined")
+            }
+        }
+
+        impl std::error::Error for Error {}
+    }
+    pub use error::Error;
+
+    /// The UTC offset in seconds
+    pub type UTCOffsetInSeconds = i32;
+
+    /// Return time offset in seconds from UTC based on the current timezone.
+    ///
+    /// Note that there may be various legitimate reasons for failure, which should be accounted for.
+    pub fn current_utc_offset() -> Result<UTCOffsetInSeconds, Error> {
+        // TODO: make this work without cfg(unsound_local_offset), see
+        // https://github.com/time-rs/time/issues/293#issuecomment-909158529
+        time::UtcOffset::current_local_offset()
+            .map(|ofs| ofs.whole_seconds())
+            .map_err(|_| Error)
+    }
 }