depfile: improve tab completion (#33773)

This PR allows you to do:

```
spack env create -d .
spack -e . add python
spack -e . concretize
spack -e . env depfile -o Makefile

make in<tab>              # -> install
make install-<tab>        # -> install-deps/
make install-deps/py<tab> # -> install-deps/python-x.y.z-hash
make install/zl<tab>      # -> install/zlib-x.y.z-hash

make SP<tab>              # -> make SPACK
make SPACK_<tab>          # -> make SPACK_INSTALL_FLAGS=
```

2 files changed, 47 insertions, 20 deletions

diff --git a/lib/spack/spack/cmd/env.py b/lib/spack/spack/cmd/env.py
index 5510c7443a..e4c62758c4 100644
--- a/lib/spack/spack/cmd/env.py
+++ b/lib/spack/spack/cmd/env.py
@@ -673,13 +673,16 @@ class MakeTargetVisitor(object):
         return ""
 
     def accept(self, node):
-        dag_hash = node.edge.spec.dag_hash()
+        fmt = "{name}-{version}-{hash}"
+        tgt = node.edge.spec.format(fmt)
         spec_str = node.edge.spec.format(
             "{name}{@version}{%compiler}{variants}{arch=architecture}"
         )
         buildcache_flag = self.build_cache_flag(node.depth)
-        prereqs = " ".join([self.target(dep.spec.dag_hash()) for dep in self.neighbors(node)])
-        self.adjacency_list.append((dag_hash, spec_str, buildcache_flag, prereqs))
+        prereqs = " ".join([self.target(dep.spec.format(fmt)) for dep in self.neighbors(node)])
+        self.adjacency_list.append(
+            (tgt, prereqs, node.edge.spec.dag_hash(), spec_str, buildcache_flag)
+        )
 
         # We already accepted this
         return True
@@ -690,6 +693,8 @@ def env_depfile(args):
     spack.cmd.require_active_env(cmd_name="env depfile")
     env = ev.active_environment()
 
+    # Special make targets are useful when including a makefile in another, and you
+    # need to "namespace" the targets to avoid conflicts.
     if args.make_target_prefix is None:
         target_prefix = os.path.join(env.env_subdir_path, "makedeps")
     else:
@@ -706,10 +711,10 @@ def env_depfile(args):
             return os.path.join(target_prefix, name)
 
     def get_install_target(name):
-        return os.path.join(target_prefix, ".install", name)
+        return os.path.join(target_prefix, "install", name)
 
     def get_install_deps_target(name):
-        return os.path.join(target_prefix, ".install-deps", name)
+        return os.path.join(target_prefix, "install-deps", name)
 
     # What things do we build when running make? By default, we build the
     # root specs. If specific specs are provided as input, we build those.
@@ -728,13 +733,22 @@ def env_depfile(args):
     )
 
     # Root specs without deps are the prereqs for the environment target
-    root_install_targets = [get_install_target(h.dag_hash()) for h in roots]
+    root_install_targets = [get_install_target(h.format("{name}-{version}-{hash}")) for h in roots]
 
-    # Cleanable targets...
-    cleanable_targets = [get_install_target(h) for h, _, _, _ in make_targets.adjacency_list]
-    cleanable_targets.extend(
-        [get_install_deps_target(h) for h, _, _, _ in make_targets.adjacency_list]
-    )
+    # All install and install-deps targets
+    all_install_related_targets = []
+
+    # Convenience shortcuts: ensure that `make install/pkg-version-hash` triggers
+    # <absolute path to env>/.spack-env/makedeps/install/pkg-version-hash in case
+    # we don't have a custom make target prefix.
+    phony_convenience_targets = []
+
+    for tgt, _, _, _, _ in make_targets.adjacency_list:
+        all_install_related_targets.append(get_install_target(tgt))
+        all_install_related_targets.append(get_install_deps_target(tgt))
+        if args.make_target_prefix is None:
+            phony_convenience_targets.append(os.path.join("install", tgt))
+            phony_convenience_targets.append(os.path.join("install-deps", tgt))
 
     buf = io.StringIO()
 
@@ -745,15 +759,17 @@ def env_depfile(args):
             "all_target": get_target("all"),
             "env_target": get_target("env"),
             "clean_target": get_target("clean"),
-            "cleanable_targets": " ".join(cleanable_targets),
+            "all_install_related_targets": " ".join(all_install_related_targets),
             "root_install_targets": " ".join(root_install_targets),
             "dirs_target": get_target("dirs"),
             "environment": env.path,
-            "install_target": get_target(".install"),
-            "install_deps_target": get_target(".install-deps"),
+            "install_target": get_target("install"),
+            "install_deps_target": get_target("install-deps"),
             "any_hash_target": get_target("%"),
             "jobserver_support": "+" if args.jobserver else "",
             "adjacency_list": make_targets.adjacency_list,
+            "phony_convenience_targets": " ".join(phony_convenience_targets),
+            "target_prefix": target_prefix,
         }
     )
 
diff --git a/share/spack/templates/depfile/Makefile b/share/spack/templates/depfile/Makefile
index dc0aeb79ea..4ff7fff0a3 100644
--- a/share/spack/templates/depfile/Makefile
+++ b/share/spack/templates/depfile/Makefile
@@ -1,4 +1,5 @@
 SPACK ?= spack
+SPACK_INSTALL_FLAGS ?=
 
 .PHONY: {{ all_target }} {{ clean_target }}
 
@@ -10,27 +11,37 @@ SPACK ?= spack
 {{ dirs_target }}:
 	@mkdir -p {{ install_target }} {{ install_deps_target }}
 
+{% if phony_convenience_targets %}
+.PHONY: {{ phony_convenience_targets }}
+{% endif %}
+
 # The spack install commands are of the form:
 # spack -e my_env --no-add --only=package --only=concrete /hash
 # This is an involved way of expressing that Spack should only install
 # an individual concrete spec from the environment without deps.
-{{ install_target }}/%: {{ install_deps_target }}/% | {{ dirs_target }}
-	{{ jobserver_support }}$(SPACK) -e '{{ environment }}' install $(SPACK_BUILDCACHE_FLAG) $(SPACK_INSTALL_FLAGS) --only-concrete --only=package --no-add /$(notdir $@) # $(SPEC)
+{{ install_target }}/%: | {{ dirs_target }}
+	{{ jobserver_support }}$(SPACK) -e '{{ environment }}' install $(SPACK_BUILDCACHE_FLAG) $(SPACK_INSTALL_FLAGS) --only-concrete --only=package --no-add /$(HASH) # $(SPEC)
 	@touch $@
 
 {{ install_deps_target }}/%: | {{ dirs_target }}
 	@touch $@
 
 # Set a human-readable SPEC variable for each target that has a hash
-{% for (parent, name, build_cache, _) in adjacency_list -%}
+{% for (parent, _, hash, name, build_cache) in adjacency_list -%}
+{{ any_hash_target }}/{{ parent }}: HASH = {{ hash }}
 {{ any_hash_target }}/{{ parent }}: SPEC = {{ name }}
 {{ any_hash_target }}/{{ parent }}: SPACK_BUILDCACHE_FLAG = {{ build_cache }}
 {% endfor %}
 
 # The Spack DAG expressed in targets:
-{% for (parent, _, _, prereqs) in adjacency_list -%}
-{{ install_deps_target }}/{{ parent }}: {{prereqs}}
+{% for (parent, prereqs, _, _, _) in adjacency_list -%}
+{{ install_target }}/{{ parent }}: {{ install_deps_target }}/{{ parent }}
+{{ install_deps_target }}/{{ parent }}: {{ prereqs }}
+{% if phony_convenience_targets %}
+install/{{ parent }}: {{ install_target }}/{{ parent }}
+install-deps/{{ parent }}: {{ install_deps_target }}/{{ parent }}
+{% endif %}
 {% endfor %}
 
 {{ clean_target }}:
-	rm -rf {{ env_target }} {{ cleanable_targets }}
+	rm -rf {{ env_target }} {{ all_install_related_targets }}