dim: Make dim sparse check each commit in the range-ish

Previously 'dim sparse' just touched all the files affected by the range
and run sparse against that. Since this may show issues from included
headers and sparse-compliance does not seem to be strongly enforced the
output is rather unhelpful.

With this change the repo is checkout at each commit, sparse is run on
incrementally, on every file that was changed.

Each result is compared to it's parent's result using remap-log to
adjust for potential line numbering changes.

Only the difference is reported.

v2:
    Clearer wording on remap-log check.
    Use the incremental build.
    Reset ref on exit.

v3:
    Make shellcheck happy:
      * Ignore SC2064 in trap
      * Quote array expansion

Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

dim

@@ -1438,15 +1438,66 @@ function dim_checkpatch
 	return $rv
 }
 
+function _restore_head_on_exit
+{
+    local original_ref
+
+    original_ref="$(git rev-parse --abbrev-ref HEAD)"
+
+    if [ "$original_ref" == "HEAD" ]; then
+        original_ref="$(git rev-parse HEAD)"
+    fi
+
+    # we want to expand this now
+    # shellcheck disable=SC2064
+    trap "git checkout -q $original_ref" EXIT
+}
+
 function dim_sparse
 {
-	local range
+	local range rv sr prev_sr prev_remapped diff_result remap_log commits
 
 	range=$(rangeish "${1:-}")
+    remap_log=$DIM_PREFIX/maintainer-tools/remap-log
 
-	make $DIM_MAKE_OPTIONS
-	touch --no-create $(git diff --name-only $range) $(git diff --name-only)
-	make C=1
+    if [ ! -e  $remap_log ]; then
+        echo "$remap_log is not compailed, please run make in maintainer-tools dir!"
+        exit 1
+    fi
+
+    _restore_head_on_exit
+
+    # make the initial reference build
+    commits=( $(git rev-list --reverse $range) )
+    git checkout --detach  ${commits[0]}~ > /dev/null 2>&1
+    make -j8 drivers/gpu/drm/ > /dev/null 2>&1
+
+	for commit in "${commits[@]}"; do
+        touch --no-create $(git diff --name-only $commit~...$commit)
+        prev_sr="$(make C=1 -j$(nproc) drivers/gpu/drm/ 2>&1 1>/dev/null | sort)"
+
+        git checkout --detach $commit >/dev/null 2>&1
+        sr="$(make C=1 -j$(nproc) drivers/gpu/drm/ 2>&1 1>/dev/null | sort)"
+
+        prev_remapped="$(echo "$prev_sr" | $remap_log <(git diff HEAD~ | $remap_log))"
+        diff_result="$(diff -u <(echo "$prev_remapped") <(echo "$sr") || true)"
+
+        echo "Commit: $(git log -n1 --format='%s' $commit)"
+        if [ -n "$diff_result" ]; then
+            echo "$diff_result" | egrep '^[+-]' | egrep -v '^[+-]{3}'
+        else
+            echo "Okay!"
+        fi
+        echo
+
+        if (echo "$diff_result" | grep -q '^+'); then
+            rv=1
+        fi
+
+        prev_sr="$sr"
+	done
+
+	return $rv
 }
 
 function dim_checker