Implemented --compact flag for rust-lang#61.

Author: ibabushkin

src/bin/cargo_semver.rs

@@ -77,7 +77,7 @@ fn main() {
         cli::exit_with_error(&config, e);
     }
 
-    if let Err(e) = run(&config, &matches, matches.opt_present("e")) {
+    if let Err(e) = run(&config, &matches) {
         cli::exit_with_error(&config, e);
     }
 }
@@ -86,10 +86,13 @@ fn main() {
 /// "stable" version, compile them both into `rlib`s, and report the breaking
 /// introduced in the "current" version with respect to the "stable" version.
 // TODO: possibly reduce the complexity by finding where some info can be taken from directly
-fn run(config: &cargo::Config, matches: &getopts::Matches, explain: bool) -> Result<()> {
+fn run(config: &cargo::Config, matches: &getopts::Matches) -> Result<()> {
     use cargo::util::important_paths::find_root_manifest_for_wd;
     debug!("running cargo-semver");
 
+    let explain = matches.opt_present("e");
+    let compact = matches.opt_present("compact");
+
     // Obtain WorkInfo for the "current"
     let current = if let Some(name_and_version) = matches.opt_str("C") {
         // -C "name:version" requires fetching the appropriate package:
@@ -170,6 +173,7 @@ fn run(config: &cargo::Config, matches: &getopts::Matches, explain: bool) -> Res
         .stdin(Stdio::piped())
         .env("RUST_SEMVER_CRATE_VERSION", stable_version)
         .env("RUST_SEMVER_VERBOSE", format!("{}", explain))
+        .env("RUST_SEMVER_COMPACT", format!("{}", compact))
         .env(
             "RUST_SEMVER_API_GUIDELINES",
             if matches.opt_present("a") {
@@ -237,6 +241,11 @@ mod cli {
             "no-default-features",
             "Do not activate the `default` feature",
         );
+        opts.optflag(
+            "",
+            "compact",
+            "Only output the suggested version on stdout for further processing",
+        );
         opts.optopt(
             "s",
             "stable-path",

src/bin/rust_semverver.rs

@@ -46,6 +46,8 @@ fn main() {
 
                     let verbose =
                         std::env::var("RUST_SEMVER_VERBOSE") == Ok("true".to_string());
+                    let compact =
+                        std::env::var("RUST_SEMVER_COMPACT") == Ok("true".to_string());
                     let api_guidelines =
                         std::env::var("RUST_SEMVER_API_GUIDELINES") == Ok("true".to_string());
                     let version = if let Ok(ver) = std::env::var("RUST_SEMVER_CRATE_VERSION") {
@@ -84,7 +86,7 @@ fn main() {
                         if let [(_, old_def_id), (_, new_def_id)] = *crates.as_slice() {
                             debug!("running semver analysis");
                             let changes = run_analysis(tcx, old_def_id, new_def_id);
-                            changes.output(tcx.sess, &version, verbose, api_guidelines);
+                            changes.output(tcx.sess, &version, verbose, compact, api_guidelines);
                         } else {
                             tcx.sess.err("could not find crate old and new crates");
                         }

src/changes.rs

@@ -879,7 +879,12 @@ impl<'tcx> ChangeSet<'tcx> {
     }
 
     /// Format the contents of a change set for user output.
-    pub fn output(&self, session: &Session, version: &str, verbose: bool, api_guidelines: bool) {
+    pub fn output(&self,
+                  session: &Session,
+                  version: &str,
+                  verbose: bool,
+                  compact: bool,
+                  api_guidelines: bool) {
         if let Ok(mut new_version) = Version::parse(version) {
             if new_version.major == 0 {
                 new_version.increment_patch();
@@ -891,10 +896,14 @@ impl<'tcx> ChangeSet<'tcx> {
                 }
             }
 
-            println!(
-                "version bump: {} -> ({}) -> {}",
-                version, self.max, new_version
-            );
+            if compact {
+                println!("{}", new_version);
+            } else {
+                println!(
+                    "version bump: {} -> ({}) -> {}",
+                    version, self.max, new_version
+                );
+            }
         } else {
             println!("max change: {}, could not parse {}", self.max, version);
         }