dependency pinning: luarocks.lock file and --pin flag

This adds support for pinning dependencies in projects and rocks:

* Adds a new flag called `--pin` which creates a `luarocks.lock`
  when building a rock with `luarocks build` or `luarocks make`.
  This lock file contains the exact version numbers of every
  direct or indirect dependency of the rock (in other words,
  it is the transitive closure of the dependencies.)
  For `make`, the `luarocks.lock` file is created in the current
  directory.
  The lock file is also installed as part of the rock in
  its metadata directory alongside its rockspec.
  When using `--pin`, if a lock file already exists, it is
  ignored and overwritten.
* When building a rock with `luarocks make`, if there is a
  `luarocks.lock` file in the current directory, the exact
  versions specified there will be used for resolving dependencies.
* When building a rock with `luarocks build`, if there is a
  `luarocks.lock` file in root of its sources, the exact
  versions specified there will be used for resolving dependencies.
* When installing a `.rock` file with `luarocks install`, if the
  rock contains a `luarocks.lock` file (i.e., if its dependencies
  were pinned with `--pin` when the rock was built), the exact
  versions specified there will be used for resolving dependencies.

8 files changed, 20 insertions, 0 deletions

diff --git a/spec/fixtures/a_repo/a_rock-2.0-1.src.rock b/spec/fixtures/a_repo/a_rock-2.0-1.src.rock
new file mode 100644
index 00000000..5824c767
--- /dev/null
+++ b/spec/fixtures/a_repo/a_rock-2.0-1.src.rock
diff --git a/spec/fixtures/a_repo/manifest b/spec/fixtures/a_repo/manifest
index 3b01b427..5ab87d25 100644
--- a/spec/fixtures/a_repo/manifest
+++ b/spec/fixtures/a_repo/manifest
@@ -19,6 +19,11 @@ repository = {
          {
             arch = "rockspec"
          }
+      },
+      ["2.0-1"] = {
+         {
+            arch = "src"
+         }
       }
    },
    busted_project = {
diff --git a/spec/fixtures/a_repo/manifest-5.1 b/spec/fixtures/a_repo/manifest-5.1
index 3b01b427..5ab87d25 100644
--- a/spec/fixtures/a_repo/manifest-5.1
+++ b/spec/fixtures/a_repo/manifest-5.1
@@ -19,6 +19,11 @@ repository = {
          {
             arch = "rockspec"
          }
+      },
+      ["2.0-1"] = {
+         {
+            arch = "src"
+         }
       }
    },
    busted_project = {
diff --git a/spec/fixtures/a_repo/manifest-5.1.zip b/spec/fixtures/a_repo/manifest-5.1.zip
index 7b53aeb0..65e316df 100644
--- a/spec/fixtures/a_repo/manifest-5.1.zip
+++ b/spec/fixtures/a_repo/manifest-5.1.zip
diff --git a/spec/fixtures/a_repo/manifest-5.2 b/spec/fixtures/a_repo/manifest-5.2
index 3b01b427..5ab87d25 100644
--- a/spec/fixtures/a_repo/manifest-5.2
+++ b/spec/fixtures/a_repo/manifest-5.2
@@ -19,6 +19,11 @@ repository = {
          {
             arch = "rockspec"
          }
+      },
+      ["2.0-1"] = {
+         {
+            arch = "src"
+         }
       }
    },
    busted_project = {
diff --git a/spec/fixtures/a_repo/manifest-5.2.zip b/spec/fixtures/a_repo/manifest-5.2.zip
index d2eddc40..b4334a65 100644
--- a/spec/fixtures/a_repo/manifest-5.2.zip
+++ b/spec/fixtures/a_repo/manifest-5.2.zip
diff --git a/spec/fixtures/a_repo/manifest-5.3 b/spec/fixtures/a_repo/manifest-5.3
index 3b01b427..5ab87d25 100644
--- a/spec/fixtures/a_repo/manifest-5.3
+++ b/spec/fixtures/a_repo/manifest-5.3
@@ -19,6 +19,11 @@ repository = {
          {
             arch = "rockspec"
          }
+      },
+      ["2.0-1"] = {
+         {
+            arch = "src"
+         }
       }
    },
    busted_project = {
diff --git a/spec/fixtures/a_repo/manifest-5.3.zip b/spec/fixtures/a_repo/manifest-5.3.zip
index 686fe232..bab15712 100644
--- a/spec/fixtures/a_repo/manifest-5.3.zip
+++ b/spec/fixtures/a_repo/manifest-5.3.zip