Bug 1375207 - Display hash from whence geckodriver came in --version; r=jgraham

Because we no longer can tag geckodriver releases in mozilla-central,
we need to include build information in the program itself.  In the
version information message displayed when passing the --version flag,
we now include the current tip's SHA1 and build date following the
version number.

This patch could be made simpler by dumping this information correctly
formatted into a text file in the output directory, but it was requested
in https://bugzilla.mozilla.org/show_bug.cgi?id=1374977 to also include
the version information in the log output, which means we need to access
it differently and in different places.

MozReview-Commit-ID: CbFQn7IV8ew

--HG--
extra : rebase_source : dcc38ba7b5f209e9878755d5d75b611e22b5253d

testing/geckodriver/build.rs

@@ -0,0 +1,73 @@
+/// Writes build information to ${OUT_DIR}/build-info.rs which is included in
+/// the program during compilation:
+///
+/// ```no_run
+/// const COMMIT_HASH: Option<&'static str> = Some("c31a366");
+/// const COMMIT_DATE: Option<&'static str> = Some("1988-05-10");
+/// ```
+///
+/// The values are `None` if running hg failed, e.g. if it is not installed or
+/// if we are not in an hg repo.
+
+use std::env;
+use std::ffi::OsStr;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+use std::process::Command;
+
+fn main() {
+    let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let mut fh = File::create(out_dir.join("build-info.rs")).unwrap();
+    writeln!(
+        fh,
+        "const COMMIT_HASH: Option<&'static str> = {:?};",
+        commit_hash()
+    ).unwrap();
+    writeln!(
+        fh,
+        "const COMMIT_DATE: Option<&'static str> = {:?};",
+        commit_date()
+    ).unwrap();
+}
+
+fn commit_hash() -> Option<String> {
+    exec(&"hg", &["log", "-r.", "-T '{node|short}'"]).or_else(
+        || {
+            exec(&"git", &["rev-parse", "HEAD"]).and_then(hg2git_sha)
+        },
+    )
+}
+
+fn commit_date() -> Option<String> {
+    exec(&"hg", &["log", "-r.", "-T '{date|isodate}'"]).or_else(|| {
+        exec(
+            &"git",
+            &["log", "-1", "--date=short", "--pretty=format:%cd"],
+        )
+    })
+}
+
+fn exec<S, I>(program: S, args: I) -> Option<String>
+where
+    S: AsRef<OsStr>,
+    I: IntoIterator<Item = S>,
+{
+    let mut cmd = Command::new(program);
+    for arg in args {
+        cmd.arg(arg.as_ref());
+    }
+    cmd.output()
+        .ok()
+        .and_then(|r| if r.status.success() {
+            Some(r.stdout)
+        } else {
+            None
+        })
+        .and_then(|o| String::from_utf8(o).ok())
+        .map(|s| s.trim_right().into())
+}
+
+fn hg2git_sha(hg_sha: String) -> Option<String> {
+    exec(&"git", &["cinnabar", "git2hg", &hg_sha])
+}

testing/geckodriver/src/main.rs

@@ -21,8 +21,10 @@ extern crate webdriver;
 extern crate log;
 
 use std::borrow::ToOwned;
+use std::fmt;
+use std::fmt::Display;
 use std::io::Write;
-use std::net::{SocketAddr, IpAddr};
+use std::net::{IpAddr, SocketAddr};
 use std::path::PathBuf;
 use std::str::FromStr;
 
@@ -45,6 +47,35 @@ mod capabilities;
 use logging::LogLevel;
 use marionette::{MarionetteHandler, MarionetteSettings, extension_routes};
 
+include!(concat!(env!("OUT_DIR"), "/build-info.rs"));
+
+struct BuildInfo;
+impl BuildInfo {
+    pub fn version() -> &'static str {
+        crate_version!()
+    }
+
+    pub fn hash() -> Option<&'static str> {
+        COMMIT_HASH
+    }
+
+    pub fn date() -> Option<&'static str> {
+        COMMIT_DATE
+    }
+}
+
+impl Display for BuildInfo {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", BuildInfo::version())?;
+        match (BuildInfo::hash(), BuildInfo::date()) {
+            (Some(hash), Some(date)) => write!(f, " ({} {})", hash, date)?,
+            (Some(hash), None) => write!(f, " ({})", hash)?,
+            _ => {},
+        }
+        Ok(())
+    }
+}
+
 type ProgramResult = std::result::Result<(), (ExitCode, String)>;
 
 enum ExitCode {
@@ -104,7 +135,7 @@ fn run() -> ProgramResult {
     let matches = app().get_matches();
 
     if matches.is_present("version") {
-        println!("geckodriver {}\n\n{}", crate_version!(),
+        println!("geckodriver {}\n\n{}", BuildInfo,
 "The source code of this program is available at
 https://github.com/mozilla/geckodriver.