context: copy symlinks as symlinks and improve error messages

src/changelog.rs

@@ -119,10 +119,24 @@ fn increment_suffix(version: &str, suffix: &str) -> String {
 pub fn parse_changelog_header(
     path: &Path,
 ) -> Result<(String, String, String), Box<dyn std::error::Error>> {
-    let file = File::open(path)?;
+    let file = File::open(path).map_err(|e| {
+        format!(
+            "Failed to read changelog '{}': {}. \
+             Make sure you are running this command from the root of a source package \
+             (a directory containing a 'debian/' subdirectory with a 'changelog' file).",
+            path.display(),
+            e
+        )
+    })?;
     let mut reader = io::BufReader::new(file);
     let mut first_line = String::new();
-    reader.read_line(&mut first_line)?;
+    reader.read_line(&mut first_line).map_err(|e| {
+        format!(
+            "Failed to read first line of changelog '{}': {}",
+            path.display(),
+            e
+        )
+    })?;
 
     // Format: package (version) series; urgency=urgency
     let re = Regex::new(r"^(\S+) \(([^)]+)\) (.*); .*")?;
@@ -132,16 +146,37 @@ pub fn parse_changelog_header(
         let series = caps.get(3).map_or("", |m| m.as_str()).to_string();
         Ok((package, version, series))
     } else {
-        Err(format!("Invalid changelog header format in {}", path.display()).into())
+        Err(format!(
+            "Invalid changelog header format in '{}'. \
+             The first line must look like: `package (version) series; urgency=...`, \
+             but got: {:?}",
+            path.display(),
+            first_line.trim_end()
+        )
+        .into())
     }
 }
 
 /// Parse a changelog file footer to extract maintainer information
 /// Returns (name, email) tuple from the last modification entry
 pub fn parse_changelog_footer(path: &Path) -> Result<(String, String), Box<dyn std::error::Error>> {
-    let mut file = File::open(path)?;
+    let mut file = File::open(path).map_err(|e| {
+        format!(
+            "Failed to read changelog '{}': {}. \
+             Make sure you are running this command from the root of a source package \
+             (a directory containing a 'debian/' subdirectory with a 'changelog' file).",
+            path.display(),
+            e
+        )
+    })?;
     let mut content = String::new();
-    file.read_to_string(&mut content)?;
+    file.read_to_string(&mut content).map_err(|e| {
+        format!(
+            "Failed to read changelog '{}': {}",
+            path.display(),
+            e
+        )
+    })?;
 
     // Find the last maintainer line (format: -- Name <email>  Date)
     let re = Regex::new(r"--\s*([^<]+?)\s*<([^>]+)>\s*")?;
@@ -159,7 +194,13 @@ pub fn parse_changelog_footer(path: &Path) -> Result<(String, String), Box<dyn s
             .to_string();
         Ok((name, email))
     } else {
-        Err(format!("No maintainer information found in {}", path.display()).into())
+        Err(format!(
+            "No maintainer information found in '{}'. \
+             The changelog must contain a line of the form '-- Name <email>  Date', \
+             but none was found.",
+            path.display()
+        )
+        .into())
     }
 }
 
@@ -283,9 +324,31 @@ fn get_maintainer_info() -> Result<(String, String), Box<dyn std::error::Error>>
     }
 
     // From git config
-    let config = git2::Config::open_default()?;
-    let name = config.get_string("user.name")?;
-    let email = config.get_string("user.email")?;
+    let config = git2::Config::open_default().map_err(|e| {
+        format!(
+            "Could not determine maintainer information. \
+             Neither $DEBFULLNAME/$DEBEMAIL nor git configuration is available: {}. \
+             Set the DEBFULLNAME and DEBEMAIL environment variables, \
+             or configure git with `git config --global user.name` and `git config --global user.email`.",
+            e
+        )
+    })?;
+    let name = config.get_string("user.name").map_err(|e| {
+        format!(
+            "Could not find git 'user.name' configuration: {}. \
+             Set it with `git config --global user.name \"Your Name\"` \
+             or define the DEBFULLNAME environment variable.",
+            e
+        )
+    })?;
+    let email = config.get_string("user.email").map_err(|e| {
+        format!(
+            "Could not find git 'user.email' configuration: {}. \
+             Set it with `git config --global user.email \"you@example.com\"` \
+             or define the DEBEMAIL environment variable.",
+            e
+        )
+    })?;
     Ok((name, email))
 }