Auto merge of #46514 - zackmdavis:sticking_it_to_the_man, r=alexcrichton

template month/year, version into man pages while building dist tarball

![the_man](https://user-images.githubusercontent.com/1076988/33596149-963956f4-d94f-11e7-926f-e683217765e5.png)

This is meant to resolve #25689.

r? @alexcrichton

Author: bors

src/bootstrap/dist.rs

@@ -28,7 +28,7 @@ use build_helper::output;
 
 use {Build, Compiler, Mode};
 use channel;
-use util::{cp_r, libdir, is_dylib, cp_filtered, copy};
+use util::{cp_r, libdir, is_dylib, cp_filtered, copy, replace_in_file};
 use builder::{Builder, RunConfig, ShouldRun, Step};
 use compile;
 use tool::{self, Tool};
@@ -434,7 +434,22 @@ impl Step for Rustc {
 
             // Man pages
             t!(fs::create_dir_all(image.join("share/man/man1")));
-            cp_r(&build.src.join("src/doc/man"), &image.join("share/man/man1"));
+            let man_src = build.src.join("src/doc/man");
+            let man_dst = image.join("share/man/man1");
+            let date_output = output(Command::new("date").arg("+%B %Y"));
+            let month_year = date_output.trim();
+            // don't use our `bootstrap::util::{copy, cp_r}`, because those try
+            // to hardlink, and we don't want to edit the source templates
+            for entry_result in t!(fs::read_dir(man_src)) {
+                let file_entry = t!(entry_result);
+                let page_src = file_entry.path();
+                let page_dst = man_dst.join(file_entry.file_name());
+                t!(fs::copy(&page_src, &page_dst));
+                // template in month/year and version number
+                replace_in_file(&page_dst,
+                                &[("<INSERT DATE HERE>", month_year),
+                                  ("<INSERT VERSION HERE>", channel::CFG_RELEASE_NUM)]);
+            }
 
             // Debugger scripts
             builder.ensure(DebuggerScripts {

src/bootstrap/util.rs

@@ -15,8 +15,8 @@
 
 use std::env;
 use std::str;
-use std::fs::{self, File};
-use std::io::{self, Read, Write};
+use std::fs::{self, File, OpenOptions};
+use std::io::{self, Read, Write, Seek, SeekFrom};
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::{SystemTime, Instant};
@@ -51,6 +51,20 @@ pub fn copy(src: &Path, dst: &Path) {
     t!(filetime::set_file_times(dst, atime, mtime));
 }
 
+/// Search-and-replaces within a file. (Not maximally efficiently: allocates a
+/// new string for each replacement.)
+pub fn replace_in_file(path: &Path, replacements: &[(&str, &str)]) {
+    let mut contents = String::new();
+    let mut file = t!(OpenOptions::new().read(true).write(true).open(path));
+    t!(file.read_to_string(&mut contents));
+    for &(target, replacement) in replacements {
+        contents = contents.replace(target, replacement);
+    }
+    t!(file.seek(SeekFrom::Start(0)));
+    t!(file.set_len(0));
+    t!(file.write_all(contents.as_bytes()));
+}
+
 pub fn read_stamp_file(stamp: &Path) -> Vec<PathBuf> {
     let mut paths = Vec::new();
     let mut contents = Vec::new();

src/doc/man/rustc.1

@@ -1,4 +1,4 @@
-.TH RUSTC "1" "September 2016" "rustc 1.13.0" "User Commands"
+.TH RUSTC "1" "<INSERT DATE HERE>" "rustc <INSERT VERSION HERE>" "User Commands"
 .SH NAME
 rustc \- The Rust compiler
 .SH SYNOPSIS

src/doc/man/rustdoc.1

@@ -1,4 +1,4 @@
-.TH RUSTDOC "1" "May 2017" "rustdoc 1.19.0" "User Commands"
+.TH RUSTDOC "1" "<INSERT DATE HERE>" "rustdoc <INSERT VERSION HERE>" "User Commands"
 .SH NAME
 rustdoc \- generate documentation from Rust source code
 .SH SYNOPSIS