Suggest cargo install --git when missing registry package looks like a git* URL

src/cargo/ops/common_for_install_and_uninstall.rs

@@ -9,12 +9,14 @@ use std::task::Poll;
 use anyhow::{bail, format_err, Context as _};
 use serde::{Deserialize, Serialize};
 use toml_edit::easy as toml;
+use url::Url;
 
 use crate::core::compiler::Freshness;
 use crate::core::{Dependency, FeatureValue, Package, PackageId, Source, SourceId};
 use crate::ops::{self, CompileFilter, CompileOptions};
 use crate::sources::PathSource;
 use crate::util::errors::CargoResult;
+use crate::util::interning::InternedString;
 use crate::util::Config;
 use crate::util::{FileLock, Filesystem};
 
@@ -520,6 +522,25 @@ pub fn path_source(source_id: SourceId, config: &Config) -> CargoResult<PathSour
     Ok(PathSource::new(&path, source_id, config))
 }
 
+fn is_package_name_a_git_url(package_name: &InternedString) -> bool {
+    if let Ok(url) = Url::parse(package_name) {
+        if let Some(domain) = url.domain() {
+            // REVIEW
+            // Are there any other git services without "git"
+            // in the domain?
+            // bitbucket?
+            // Is it possible to ask the cargo/crates team for
+            // some stats where crates projects are currently hosted on
+            return domain.contains("git");
+        }
+    }
+    false
+}
+
+fn was_git_url_miscategorised_as_a_registry_dep(dep: &Dependency) -> bool {
+    return dep.source_id().is_registry() && is_package_name_a_git_url(&dep.package_name());
+}
+
 /// Gets a Package based on command-line requirements.
 pub fn select_dep_pkg<T>(
     source: &mut T,
@@ -565,12 +586,22 @@ where
                     source.source_id()
                 )
             } else {
-                bail!(
-                    "could not find `{}` in {} with version `{}`",
-                    dep.package_name(),
-                    source.source_id(),
-                    dep.version_req(),
-                )
+                if was_git_url_miscategorised_as_a_registry_dep(&dep) {
+                    bail!(
+                        "could not find `{}` in {} with version `{}`. Try adding `--git {}`",
+                        dep.package_name(),
+                        source.source_id(),
+                        dep.version_req(),
+                        dep.package_name(),
+                    )
+                } else {
+                    bail!(
+                        "could not find `{}` in {} with version `{}`",
+                        dep.package_name(),
+                        source.source_id(),
+                        dep.version_req(),
+                    )
+                }
             }
         }
     }

tests/testsuite/install.rs

@@ -1418,6 +1418,19 @@ fn test_install_git_cannot_be_a_base_url() {
         .run();
 }
 
+#[cargo_test]
+fn test_install_from_git_generate_suggestion() {
+    registry::init();
+    cargo_process("install https://github.com/rust-lang/cargo")
+        .with_status(101)
+        .with_stderr(
+            "\
+[UPDATING] `[..]` index
+error: could not find `https://github.com/rust-lang/cargo` in registry `crates-io` with version `*`. Try adding `--git https://github.com/rust-lang/cargo`",
+        )
+        .run();
+}
+
 #[cargo_test]
 fn uninstall_multiple_and_specifying_bin() {
     cargo_process("uninstall foo bar --bin baz")