Add the query-deps family of targets2020.03.05

The query-deps, query-doc-deps, query-rel-deps, query-test-deps
and query-shell-deps targets go through dependencies and print
some information about them:

  $ make query-deps
  ...
  cowboy: cowlib git https://github.com/ninenines/cowlib 2.7.3
  cowboy: ranch git https://github.com/ninenines/ranch 1.7.1

  $ make query-deps QUERY="name repo version absolute_path"
  ...
  cowboy: cowlib https://github.com/ninenines/cowlib 2.7.3 /path/to/deps/cowlib
  cowboy: ranch https://github.com/ninenines/ranch 1.7.1 /path/to/deps/ranch

The query-deps target is recursive; the others aren't. This
mirrors the behavior when fetching and building dependencies.

The full list of options is:

  QUERY="fetch_method name repo version extra absolute_path"

When an option has no corresponding value, "-" will be printed.
For example most fetch methods do not have extra information to
print. When there is extra information, the value will be prefixed
with a descriptive name. For example: package-name=uuid_erl

This commit also introduces changes to deps handling: some of
the functions for querying will now be used directly. In the
future the goal is to remove the old dep_name, dep_commit, etc.
functions and replace their usage with the new query functions.

Custom fetch methods should implement query functions in order
to have information about the relevant dependencies printed
properly.

1 files changed, 42 insertions, 0 deletions

diff --git a/doc/src/guide/deps.asciidoc b/doc/src/guide/deps.asciidoc
index 11f09fa..066a3d8 100644
--- a/doc/src/guide/deps.asciidoc
+++ b/doc/src/guide/deps.asciidoc
@@ -180,6 +180,7 @@ The following table lists all existing methods:
 | hex            | hex version [pkg] | Download the given project version from hex.pm
 | fail           | N/A               | Always fail, reserved for internal use
 | legacy         | N/A               | Legacy Erlang.mk fetcher, reserved for internal use
+| default        | N/A               | Reserved
 |===
 
 The `git` and `hg` methods both have a repository and commit.
@@ -369,6 +370,47 @@ 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.
 
+=== Querying dependencies
+
+You can obtain information about all dependencies with
+the `make query-deps` family of commands:
+
+* `make query-deps` will list dependencies found in `BUILD_DEPS`
+  and `DEPS` recursively.
+* `make query-doc-deps` will list documentation dependencies
+  of the current project.
+* `make query-rel-deps` will list release dependencies
+  of the current project.
+* `make query-shell-deps` will list shell dependencies
+  of the current project.
+* `make query-test-deps` will list test dependencies
+  of the current project.
+
+By default the information printed will be the dependency name,
+fetch method, repository and version, prefixed by the current
+project's name. But this output can be customized via the
+variable `QUERY`:
+
+[source,bash]
+$ make query-deps QUERY="name fetch_method repo version extra absolute_path"
+
+The following options are available:
+
+name:: The dependency name.
+fetch_method:: The dependency's fetch method.
+repo:: The dependency's repository.
+version:: The dependency's version, tag or commit.
+extra:: Any additional information specific to the fetch method used.
+absolute_path:: The dependency's location after it has been fetched.
+
+Fields that have no value will print `-`. For example
+not all fetch methods have a value for the `version`.
+
+The value for `extra`, when available, will be formatted
+with the name of the information printed prefixed. For
+example the hex fetch method will add
+`package-name=uuid_erl` for the `uuid` application.
+
 === Ignoring unwanted dependencies
 
 Sometimes, you may want to ignore dependencies entirely.