core/deps-tools.mk: New targets `fetch-deps` and `list-deps`

.. to fetch and list deps recurvively.

Therefore, they work on direct dependencies, dependencies' dependencies,
and so on. Nothing is built with those targets.

The following targets are also available to work on other kinds of
dependencies:
    make fetch-doc-deps
    make fetch-rel-deps
    make fetch-test-deps
    make fetch-shell-deps
    make list-doc-deps
    make list-rel-deps
    make list-test-deps
    make list-shell-deps

In all cases, they include "normal" and eg. "test" dependencies of the
top-level project, then only "normal" dependencies' dependencies.

It's possible to include several kinds in one go:
    make fetch-deps DEP_TYPES='doc test'
    make list-deps DEP_TYPES='doc test'

As it may be difficult to use the output of `make list-*` because
the list could appear after other targets output (like dependencies
fetching), the list is available in files pointed by the following
variables:
    $(ERLANG_MK_RECURSIVE_DEPS_LIST)
    $(ERLANG_MK_RECURSIVE_DOC_DEPS_LIST)
    $(ERLANG_MK_RECURSIVE_REL_DEPS_LIST)
    $(ERLANG_MK_RECURSIVE_TEST_DEPS_LIST)
    $(ERLANG_MK_RECURSIVE_SHELL_DEPS_LIST)

Internally, `list-deps` is simply implemented on top of `fetch-deps`:
the latter fills a sorted log with all the directories it traversed.
`list-deps` finally just prints the log file to stdout.

Fixes #560.

1 files changed, 49 insertions, 0 deletions

diff --git a/doc/src/guide/deps.asciidoc b/doc/src/guide/deps.asciidoc
index eb6f2f0..723deb0 100644
--- a/doc/src/guide/deps.asciidoc
+++ b/doc/src/guide/deps.asciidoc
@@ -286,6 +286,55 @@ different version of D, it will always be A's version
 that wins, because we fetch all dependencies of A before
 fetching those from B or C.
 
+=== Fetching and listing dependencies only
+
+You can fetch all dependencies recursively without building anything,
+with the `make fetch-deps` command. It follows the same rules described
+in the section above.
+
+You can list all dependencies recursively, again without building
+anything, with the `make list-deps` command. It will obviously need
+to fetch all dependencies exactly like `make fetch-deps`. Once
+everything is fetched, it prints a sorted list of absolute paths to the
+dependencies.
+
+By default, `fetch-deps` and `list-deps` work on the `BUILD_DEPS`
+and `DEPS` lists only. To also fetch/list `TEST_DEPS`, `DOC_DEPS`,
+`REL_DEPS` and/or `SHELL_DEPS`, you have two possibilities:
+
+* You can use `make fetch-test-deps`, `make fetch-doc-deps`, `make
+  fetch-rel-deps` and `make fetch-shell-deps` commands respectively.
+  If you want to list them, you can use `make list-test-deps`, `make
+  list-doc-deps`, `make list-rel-deps` and `make list-shell-deps`
+  respectively.
+* You can use `make fetch-deps` or `make list-deps` with the Makefile
+  variable `DEP_TYPES` set to a list of dependency types you want.
+  The types are `test`, `doc`, `rel` and `shell` respectively. For
+  example, you can list test and doc dependencies with `make list-deps
+  DEP_TYPES='test doc'`.
+
+Note that only first level `TEST_DEPS`, `DOC_DEPS`, `REL_DEPS` and
+`SHELL_DEPS` are included, not dependencies' one. In other word,
+`make list-test-deps` lists the `TEST_DEPS` of your project, but not
+`TEST_DEPS` of the projects yours depend on.
+
+No matter which method you use, `BUILD_DEPS` and `DEPS` are always
+included.
+
+Internally, the `make fetch-*` commands store the complete list of
+dependencies in files named `$(ERLANG_MK_RECURSIVE_DEPS_LIST)`,
+`$(ERLANG_MK_RECURSIVE_TEST_DEPS_LIST)`,
+`$(ERLANG_MK_RECURSIVE_DOC_DEPS_LIST)`,
+`$(ERLANG_MK_RECURSIVE_REL_DEPS_LIST)` and
+`$(ERLANG_MK_RECURSIVE_SHELL_DEPS_LIST)`. Those files are simply printed
+by the `make list-*` commands.
+
+`make list-*` commands are made for human beings. If you need the list
+of dependencies in a Makefile or a script, you should use the content
+of those files directly instead. The reason is that `make fetch-*` and
+`make list-*` may have unwanted content in their output, such as actual
+fetching of dependencies.
+
 === Ignoring unwanted dependencies
 
 Sometimes, you may want to ignore dependencies entirely.