git-r3.eclass: Support checking out specific subdirectories

Support limiting the git checkout to specific subdirectories of the git
tree, using 'git checkout ... -- <paths>...' The main use case for this
is doing partial checkouts of very large repositories where only a small
subset of files is necessary. Doing partial checkouts can save both
time and disk space which can be important in large intertwined
projects such as LLVM+Clang.

diff --git a/eclass/git-r3.eclass b/eclass/git-r3.eclass
index c9d2731a64fec1214d63e59d6d136fdd2adeb1a4..caf4e8d003e0d34f909efbee0d4e9679519c9cf4 100644 (file)
--- a/eclass/git-r3.eclass
+++ b/eclass/git-r3.eclass
@@ -803,7 +803,7 @@ git-r3_fetch() {
 }
 
 # @FUNCTION: git-r3_checkout
-# @USAGE: [<repo-uri> [<checkout-path> [<local-id>]]]
+# @USAGE: [<repo-uri> [<checkout-path> [<local-id> [<checkout-paths>...]]]]
 # @DESCRIPTION:
 # Check the previously fetched tree to the working copy.
 #
@@ -819,6 +819,12 @@ git-r3_fetch() {
 # <local-id> needs to specify the local identifier that was used
 # for respective git-r3_fetch.
 #
+# If <checkout-paths> are specified, then the specified paths are passed
+# to 'git checkout' to effect a partial checkout. Please note that such
+# checkout will not cause the repository to switch branches,
+# and submodules will be skipped at the moment. The submodules matching
+# those paths might be checked out in a future version of the eclass.
+#
 # The checkout operation will write to the working copy, and export
 # the repository state into the environment. If the repository contains
 # submodules, they will be checked out recursively.
@@ -836,6 +842,7 @@ git-r3_checkout() {
 
        local out_dir=${2:-${EGIT_CHECKOUT_DIR:-${WORKDIR}/${P}}}
        local local_id=${3:-${CATEGORY}/${PN}/${SLOT%/*}}
+       local checkout_paths=( "${@:4}" )
 
        local -x GIT_DIR
        _git-r3_set_gitdir "${repos[0]}"
@@ -883,6 +890,9 @@ git-r3_checkout() {
                else
                        set -- "${@}" "${new_commit_id}"
                fi
+               if [[ ${checkout_paths[@]} ]]; then
+                       set -- "${@}" -- "${checkout_paths[@]}"
+               fi
                echo "${@}" >&2
                "${@}" || die "git checkout ${remote_ref:-${new_commit_id}} failed"
        }
@@ -905,8 +915,12 @@ git-r3_checkout() {
                        echo "   updating from commit:     ${old_commit_id}"
                        echo "   to commit:                ${new_commit_id}"
 
-                       git --no-pager diff --stat \
+                       set -- git --no-pager diff --stat \
                                ${old_commit_id}..${new_commit_id}
+                       if [[ ${checkout_paths[@]} ]]; then
+                               set -- "${@}" -- "${checkout_paths[@]}"
+                       fi
+                       "${@}"
                else
                        echo "   at the commit:            ${new_commit_id}"
                fi
@@ -914,7 +928,7 @@ git-r3_checkout() {
        git update-ref --no-deref refs/git-r3/"${local_id}"/{__old__,__main__} || die
 
        # recursively checkout submodules
-       if [[ -f ${out_dir}/.gitmodules ]]; then
+       if [[ -f ${out_dir}/.gitmodules && ! ${checkout_paths} ]]; then
                local submodules
                _git-r3_set_submodules \
                        "$(<"${out_dir}"/.gitmodules)"