Add information package caching.

Per https://github.com/rust-lang/cargo/issues/1609
Added in a single line that states that the cached packages are only
removed by running the clean command.

diff --git a/src/doc/environment-variables.md b/src/doc/environment-variables.md
index 0b40f0bc01b43205d8eb2f7cbdf054c15e3baf52..250083a24d8e29188db4d153edd18a1f57d14f9c 100644 (file)
--- a/src/doc/environment-variables.md
+++ b/src/doc/environment-variables.md
@@ -15,7 +15,8 @@ Here are a list of the variables Cargo sets, organized by when it sets them:
 
 * `CARGO_HOME` - Cargo maintains a local cache of the registry index and of git
   checkouts of crates.  By default these are stored under `$HOME/.cargo`, but
-  this variable overrides the location of this directory.
+  this variable overrides the location of this directory. Once a
+  crate is cached it is only removed by the clean command.
 * `CARGO_PROFILE` - If this is set to a positive integer *N*, Cargo will record
   timing data as it runs.  When it exits, it will print this data as a profile
   *N* levels deep.