Install pre-release versions by default for git deps

closes #5627

Author: matklad

src/cargo/ops/cargo_install.rs

@@ -480,9 +480,16 @@ where
                 None => None,
             };
             let vers = vers.as_ref().map(|s| &**s);
+            let vers_spec = if vers.is_none() && source.source_id().is_registry() {
+                // Avoid pre-release versions from crate.io
+                // unless explicitly asked for
+                Some("*")
+            } else {
+                vers
+            };
             let dep = Dependency::parse_no_deprecated(
                 name,
-                Some(vers.unwrap_or("*")),
+                vers_spec,
                 source.source_id(),
             )?;
             let deps = source.query_vec(&dep)?;

tests/testsuite/install.rs

@@ -138,6 +138,31 @@ warning: be sure to add `[..]` to your PATH to be able to run the installed bina
     assert_that(cargo_home(), has_installed_exe("foo"));
 }
 
+#[test]
+fn installs_beta_version_by_explicit_name_from_git() {
+    let p = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.3.0-beta.1"
+            authors = []
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    assert_that(
+        cargo_process("install")
+            .arg("--git")
+            .arg(p.url().to_string())
+            .arg("foo"),
+        execs().with_status(0),
+    );
+    assert_that(cargo_home(), has_installed_exe("foo"));
+}
+
 #[test]
 fn missing() {
     pkg("foo", "0.0.1");