Auto merge of #2296 - alexcrichton:wow-thats-a-bad-bug, r=brson

There was a previous bug where if any crate's name was the start of the crate
being updated that the crate wouldn't resolve at all, and this fixes the prefix
checking error bug.

cc #2293

Author: bors

src/cargo/sources/registry.rs

@@ -505,7 +505,8 @@ impl<'cfg> Registry for RegistrySource<'cfg> {
         // version requested (agument to `--precise`).
         summaries.retain(|s| {
             match self.source_id.precise() {
-                Some(p) if p.starts_with(dep.name()) => {
+                Some(p) if p.starts_with(dep.name()) &&
+                           p[dep.name().len()..].starts_with("=") => {
                     let vers = &p[dep.name().len() + 1..];
                     s.version().to_string() == vers
                 }

tests/test_cargo_registry.rs

@@ -932,3 +932,27 @@ test!(bundled_crate_in_registry {
 
     assert_that(p.cargo("run"), execs().with_status(0));
 });
+
+test!(update_same_prefix_oh_my_how_was_this_a_bug {
+    let p = project("foo")
+        .file("Cargo.toml", r#"
+            [project]
+            name = "ugh"
+            version = "0.5.0"
+            authors = []
+
+            [dependencies]
+            foo = "0.1"
+        "#)
+        .file("src/main.rs", "fn main() {}");
+    p.build();
+
+    Package::new("foobar", "0.2.0").publish();
+    Package::new("foo", "0.1.0")
+        .dep("foobar", "0.2.0")
+        .publish();
+
+    assert_that(p.cargo("generate-lockfile"), execs().with_status(0));
+    assert_that(p.cargo("update").arg("-pfoobar").arg("--precise=0.2.0"),
+                execs().with_status(0));
+});