Improve the cargo install deprecation messaging

src/bin/cargo/commands/install.rs

@@ -60,9 +60,10 @@ By default cargo will refuse to overwrite existing binaries. The `--force` flag
 enables overwriting existing binaries. Thus you can reinstall a crate with
 `cargo install --force <crate>`.
 
-As a special convenience, omitting the <crate> specification entirely will
+Omitting the <crate> specification entirely will
 install the crate in the current directory. That is, `install` is equivalent to
-the more explicit `install --path .`.
+the more explicit `install --path .`.  This behaviour is deprecated, and no
+longer supported as of the Rust 2018 edition.
 
 If the source is crates.io or `--git` then by default the crate will be built
 in a temporary target directory.  To avoid this, the target directory can be

src/cargo/ops/cargo_install.rs

@@ -237,15 +237,16 @@ fn install_one(
     if from_cwd {
         match pkg.manifest().edition() {
             Edition::Edition2015 => config.shell().warn(
-                "To build the current package use `cargo build`, \
-                 to install the current package run `cargo install --path .`",
+                "Using `cargo install` to install the binaries for the \
+                 project in current working directory is deprecated, \
+                 use `cargo install --path .` instead. \
+                 Use `cargo build` if you want to simply build the package.",
             )?,
             Edition::Edition2018 => bail!(
-                "To build the current package use `cargo build`, \
-                 to install the current package run `cargo install --path .`, \
-                 otherwise specify a crate to install from \
-                 crates.io, or use --path or --git to \
-                 specify alternate source"
+                "Using `cargo install` to install the binaries for the \
+                 project in current working directory is no longer supported, \
+                 use `cargo install --path .` instead. \
+                 Use `cargo build` if you want to simply build the package."
             ),
         }
     };

tests/testsuite/install.rs

@@ -785,9 +785,10 @@ fn installs_from_cwd_by_default() {
     assert_that(
         cargo_process("install").cwd(p.root()),
         execs().with_stderr_contains(
-                "\
-warning: To build the current package use `cargo build`, to install the current package run `cargo install --path .`
-",
+            "warning: Using `cargo install` to install the binaries for the \
+             project in current working directory is deprecated, \
+             use `cargo install --path .` instead. \
+             Use `cargo build` if you want to simply build the package.",
         ),
     );
     assert_that(cargo_home(), has_installed_exe("foo"));
@@ -819,11 +820,10 @@ fn installs_from_cwd_with_2018_warnings() {
     assert_that(
         cargo_process("install").cwd(p.root()).masquerade_as_nightly_cargo(),
         execs().with_status(101).with_stderr_contains(
-            "error: To build the current package use `cargo build`, \
-             to install the current package run `cargo install --path .`, \
-             otherwise specify a crate to install from crates.io, \
-             or use --path or --git to specify alternate source\
-             ",
+            "error: Using `cargo install` to install the binaries for the \
+             project in current working directory is no longer supported, \
+             use `cargo install --path .` instead. \
+             Use `cargo build` if you want to simply build the package.",
         ),
     );
     assert_that(cargo_home(), is_not(has_installed_exe("foo")));