support equivalent to tar's --clamp-mtime

src/header.rs

@@ -49,6 +49,13 @@ pub enum HeaderMode {
     /// Only metadata that is directly relevant to the identity of a file will
     /// be included. In particular, ownership and mod/access times are excluded.
     Deterministic,
+
+    #[cfg(unix)]
+    /// All supported metadata, including mod tims and ownership will
+    /// be included, but mod times greater than the specified value will
+    /// use the specified value instead. This mimics GNU tar's
+    /// `--clamp-mtime` option.
+    ClampMtime(u64),
 }
 
 /// Representation of the header of an entry in an archive
@@ -796,6 +803,17 @@ impl Header {
                 };
                 self.set_mode(fs_mode);
             }
+            #[cfg(unix)]
+            HeaderMode::ClampMtime(clamp) => {
+                self.set_mtime(if meta.mtime() as u64 > clamp {
+                    clamp
+                } else {
+                    meta.mtime() as u64
+                });
+                self.set_uid(meta.uid() as u64);
+                self.set_gid(meta.gid() as u64);
+                self.set_mode(meta.mode());
+            }
         }
 
         // Note that if we are a GNU header we *could* set atime/ctime, except

tests/all.rs

@@ -799,6 +799,40 @@ fn zero_file_times() {
     assert!(atime.unix_seconds() != 0);
 }
 
+#[test]
+#[cfg(unix)]
+fn clamp_mtime() {
+    let td = t!(TempBuilder::new().prefix("tar-rs").tempdir());
+
+    let clamp = 1000000000;
+    let max_clamp = u64::MAX;
+
+    let mut ar = Builder::new(Vec::new());
+    ar.mode(HeaderMode::ClampMtime(clamp));
+    let path = td.path().join("tmpfile");
+    t!(File::create(&path));
+    t!(ar.append_path_with_name(&path, "a"));
+
+    ar.mode(HeaderMode::ClampMtime(max_clamp));
+    t!(ar.append_path_with_name(&path, "b"));
+
+    let data = t!(ar.into_inner());
+    let mut ar = Archive::new(&data[..]);
+    assert!(ar.unpack(td.path()).is_ok());
+
+    let meta = fs::metadata(td.path().join("a")).unwrap();
+    let mtime = FileTime::from_last_modification_time(&meta);
+    let atime = FileTime::from_last_access_time(&meta);
+    assert!(mtime.unix_seconds() as u64 == clamp);
+    assert!(atime.unix_seconds() as u64 == clamp);
+
+    let meta = fs::metadata(td.path().join("b")).unwrap();
+    let mtime = FileTime::from_last_modification_time(&meta);
+    let atime = FileTime::from_last_access_time(&meta);
+    assert!((mtime.unix_seconds() as u64) < max_clamp);
+    assert!((atime.unix_seconds() as u64) < max_clamp);
+}
+
 #[test]
 fn backslash_treated_well() {
     // Insert a file into an archive with a backslash