Allow adding files to a package without needing a file on disk

closes #207

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `Dependency::config()`, `Dependency::user()`, `Dependency::group()`
 - `PackageBuilder::verify_script()`
 - `PackageBuilder::group()` and `PackageBuilder::packager()`
+- `PackageBuilder::with_file_contents()`
 - Added support for the automatic user/group creation feature in rpm 4.19
 
 ### Changed

src/rpm/builder.rs

@@ -363,6 +363,40 @@ impl PackageBuilder {
         Ok(self)
     }
 
+    /// Add a file to the package without needing an existing file.
+    ///
+    /// Helpful if files are being generated on-demand, and you don't want to write them to disk.
+    ///
+    /// ```
+    /// # fn foo() -> Result<(), Box<dyn std::error::Error>> {
+    ///
+    /// let pkg = rpm::PackageBuilder::new("foo", "1.0.0", "Apache-2.0", "x86_64", "some baz package")
+    ///     .with_file_contents(
+    ///         "
+    /// [check]
+    /// date = true
+    /// time = true
+    /// ",
+    ///         rpm::FileOptions::new("/etc/awesome/config.toml").is_config(),
+    ///     )?
+    ///      .with_file_contents(
+    ///         "./awesome-config.toml",
+    ///         // you can set a custom mode, capabilities and custom user too
+    ///         rpm::FileOptions::new("/etc/awesome/second.toml").mode(0o100744).caps("cap_sys_admin=pe")?.user("hugo"),
+    ///     )?
+    ///     .build()?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn with_file_contents(
+        mut self,
+        content: impl Into<Vec<u8>>,
+        options: impl Into<FileOptions>,
+    ) -> Result<Self, Error> {
+        self.add_data(content.into(), Timestamp::now(), options.into())?;
+        Ok(self)
+    }
+
     fn add_data(
         &mut self,
         content: Vec<u8>,