with directory with autodetection of crate

When adding a dependency as a pinned dir, and the target dir is a regular Alire
crate, we can autodetect the crate we are adding as dependency. In that case
the command becomes `alr with --url <url>`. This can also be useful in the
future for remote URLs that will also provide the crate being retrieved.

doc/user-changes.md

@@ -4,6 +4,19 @@ This document is a development diary summarizing changes in `alr` that notably
 affect the user experience. It is intended as a one-stop point for users to
 stay on top of `alr` new features.
 
+## Use crate metadata when pinning to a directory
+
+PR [#450](https://github.com/alire-project/alire/pull/450).
+
+When pinning a dependency to a directory (`alr pin|with <crate> --url`), detect
+if the target contains Alire metadata (as usual, in an `alire` subdir). In that
+case, use it to determine further dependencies and project file scopes. Also,
+the target dependency name is verified.
+
+For such a target directory, a shortcut `with` command is available since the
+crate name can be determined from the metadata: `alr with --url
+/path/to/target` (note the absence of a crate name).
+
 ## Allow working with incomplete solutions
 
 PR [#447](https://github.com/alire-project/alire/pull/447).

src/alire/alire-roots.adb

@@ -1,3 +1,5 @@
+with Ada.Directories;
+
 with Alire.Directories;
 with Alire.Root;
 with Alire.TOML_Index;
@@ -33,7 +35,7 @@ package body Alire.Roots is
                --  Crate loaded properly, we can return a valid root here
                Trace.Debug ("Valid root found at " & Path);
                return New_Root (R    => Release,
-                                Path => Path,
+                                Path => Ada.Directories.Full_Name (Path),
                                 Env  => Alire.Root.Platform_Properties);
             end;
          else

src/alr/alr-commands-withing.adb

@@ -73,17 +73,13 @@ package body Alr.Commands.Withing is
    -- Add_Softlink --
    ------------------
 
-   procedure Add_Softlink (Cmd : Command) is
+   procedure Add_Softlink (Dep_Spec : String;
+                           Path     : String) is
       Requested : constant Alire.Milestones.Allowed_Milestones :=
-                    Alire.Milestones.Crate_Versions (Argument (1));
+                    Alire.Milestones.Crate_Versions (Dep_Spec);
       New_Dep   : constant Alire.Dependencies.Dependency :=
                     Alire.Dependencies.From_Milestones (Requested);
    begin
-      if Num_Arguments /= 1 then
-         Reportaise_Wrong_Arguments
-           ("Exactly one crate needed for external pinning.");
-      end if;
-
       declare
          use Alire;
          use type Conditional.Dependencies;
@@ -94,7 +90,7 @@ package body Alr.Commands.Withing is
                           Old_Solution
                             .Depending_On (New_Dep)
                             .Linking (Crate => New_Dep.Crate,
-                                      Path  => Cmd.URL.all);
+                                      Path  => Path);
       begin
 
          --  Prevent double-add
@@ -124,6 +120,25 @@ package body Alr.Commands.Withing is
       end;
    end Add_Softlink;
 
+   ---------------------
+   -- Detect_Softlink --
+   ---------------------
+
+   procedure Detect_Softlink (Path : String) is
+      Root : constant Alire.Roots.Root := Alire.Roots.Detect_Root (Path);
+   begin
+      if Root.Is_Valid then
+         --  Add a dependency on ^(detected version) (i.e., safely upgradable)
+         Add_Softlink
+           (Dep_Spec => Root.Release.Name_Str
+                        & "^" & Root.Release.Version.Image,
+            Path     => Path);
+      else
+         Reportaise_Command_Failed
+           ("cannot add target: " & Root.Invalid_Reason);
+      end if;
+   end Detect_Softlink;
+
    ---------
    -- Del --
    ---------
@@ -432,10 +447,10 @@ package body Alr.Commands.Withing is
 
          if Cmd.URL.all /= "" then
             if Num_Arguments = 1 then
-               Add_Softlink (Cmd);
+               Add_Softlink (Dep_Spec => Argument (1),
+                             Path     => Cmd.URL.all);
             else
-               raise Alire.Unimplemented;
-               --  TODO: detect crate at given path, and use it
+               Detect_Softlink (Cmd.URL.all);
             end if;
          else
             Requires_Full_Index;

testsuite/tests/with/pin-dir-crate-autodetect/test.py

@@ -0,0 +1,36 @@
+"""
+Test that `alr with --url` without explicit crate autodetects the target crate
+and correctly adds the pinned dependency
+"""
+
+import os
+import re
+
+from drivers.alr import run_alr
+from drivers.asserts import assert_match
+from drivers.helpers import path_separator
+from glob import glob
+
+# Retrieve a crate
+run_alr('get', 'hello=1')
+target = glob('hello*')[0]
+
+# Initialize a workspace
+run_alr('init', '--bin', 'xxx')
+os.chdir('xxx')
+
+# Add the directory as pinned crate, with autodetection (no crate given,
+# inferred from the crate metadata found at target).
+run_alr('with', '--url', '..' + path_separator() + target)
+
+# Verify that hello^1 is a new dependency and also that hello dependencies are
+# in the solution.
+p = run_alr('with', '--solve')
+assert_match('''Dependencies \(direct\):
+   hello\^1\.0\.0
+.*Dependencies \(solution\):
+   hello=1\.0\.0 .*
+   libhello=1\.1\.0 .*''',  # we skip non-relevant details
+             p.out, flags=re.S)
+
+print('SUCCESS')

testsuite/tests/with/pin-dir-crate-autodetect/test.yaml

@@ -0,0 +1,4 @@
+driver: python-script
+indexes:
+    solver_index:
+        in_fixtures: true