git: add support for shallow recommendations

In more recent versions of git, the .gitmodules file can
be configured to recommend if a submodule should be cloned as
shallow or not. Add support for this feature since it gives the
rock maintainer more control over which submodules should be shallow
cloned.

The rock maintainer may set the boolean `shallow` to true or false in
.gitmodules. If omitted it is treated as false.

Signed-off-by: Pedro Tammela <pctammela@gmail.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/src/luarocks/fetch/git.lua b/src/luarocks/fetch/git.lua
index 49ee7183..88ba4848 100644
--- a/src/luarocks/fetch/git.lua
+++ b/src/luarocks/fetch/git.lua
@@ -50,6 +50,13 @@ local function git_supports_shallow_submodules(git_cmd)
    return git_is_at_least(git_cmd, "1.8.4")
 end
 
+--- Git >= 2.10 can fetch submodules shallowly according to .gitmodules configuration, allowing more granularity.
+-- @param git_cmd string: name of git command.
+-- @return boolean: Whether Git can fetch submodules shallowly according to .gitmodules.
+local function git_supports_shallow_recommendations(git_cmd)
+   return git_is_at_least(git_cmd, "2.10.0")
+end
+
 local function git_identifier(git_cmd, ver)
    if not (ver:match("^dev%-%d+$") or ver:match("^scm%-%d+$")) then
       return nil
@@ -132,7 +139,9 @@ function git.get_sources(rockspec, extract, dest_dir, depth)
    if rockspec:format_is_at_least("3.0") then
       command = {fs.Q(git_cmd), "submodule", "update", "--init", "--recursive"}
 
-      if git_supports_shallow_submodules(git_cmd) then
+      if git_supports_shallow_recommendations(git_cmd) then
+         table.insert(command, 5, "--recommend-shallow")
+      elseif git_supports_shallow_submodules(git_cmd) then
          -- Fetch only the last commit of each submodule.
          table.insert(command, 5, "--depth=1")
       end