Introduce term-size dependency and consider term width when trimming

Author: estebank

Cargo.lock

@@ -3219,6 +3219,7 @@ dependencies = [
  "rustc_data_structures",
  "serialize",
  "syntax_pos",
+ "term_size",
  "termcolor",
  "unicode-width",
 ]
@@ -4090,6 +4091,17 @@ dependencies = [
  "winapi 0.3.6",
 ]
 
+[[package]]
+name = "term_size"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e5b9a66db815dcfd2da92db471106457082577c3c278d4138ab3e3b4e189327"
+dependencies = [
+ "kernel32-sys",
+ "libc",
+ "winapi 0.2.8",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.0.4"

src/librustc_errors/Cargo.toml

@@ -18,3 +18,4 @@ unicode-width = "0.1.4"
 atty = "0.2"
 termcolor = "1.0"
 annotate-snippets = "0.6.1"
+term_size = "0.3.1"