spack install: simplify behavior when inside environments (#35206)

Example one:

```
spack install --add x y z
```

is equivalent to

```
spack add x y z
spack concretize
spack install --only-concrete
```

where `--only-concrete` installs without modifying spack.yaml/spack.lock

Example two:

```
spack install
```

concretizes current spack.yaml if outdated and installs all specs.

Example three:

```
spack install x y z
```

concretizes current spack.yaml if outdated and installs *only* concrete
specs in the environment that match abstract specs `x`, `y`, or `z`.

1 files changed, 2 insertions, 2 deletions

diff --git a/share/spack/templates/depfile/Makefile b/share/spack/templates/depfile/Makefile
index 3e844176bc..a50304a8be 100644
--- a/share/spack/templates/depfile/Makefile
+++ b/share/spack/templates/depfile/Makefile
@@ -19,11 +19,11 @@ SPACK_INSTALL_FLAGS ?=
 {% endif %}
 
 # The spack install commands are of the form:
-# spack -e my_env --no-add --only=package --only=concrete /hash
+# spack -e my_env --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 }}/%: | {{ dirs_target }}
-	{{ jobserver_support }}$(SPACK) -e '{{ environment }}' install $(SPACK_BUILDCACHE_FLAG) $(SPACK_INSTALL_FLAGS) --only-concrete --only=package --no-add /$(HASH) # $(SPEC)
+	{{ jobserver_support }}$(SPACK) -e '{{ environment }}' install $(SPACK_BUILDCACHE_FLAG) $(SPACK_INSTALL_FLAGS) --only-concrete --only=package /$(HASH) # $(SPEC)
 	@touch $@
 
 {{ install_deps_target }}/%: | {{ dirs_target }}