Skylark repositories: support additional arguments for the patch tool

Instead of hard-coding "-p0", allow the arguments for that patch tool
to be overridden. In particular, this supports the use case of patches
generated with `git format-patch` which are to be read as `-p1`.

Improves on #5379.
Closes #4974 as superseded.

Change-Id: I809fde14beab21d8a755ba4f1706b602bae3c1bb
PiperOrigin-RevId: 200373909

4 files changed, 66 insertions, 1 deletions

diff --git a/src/test/shell/bazel/external_patching_test.sh b/src/test/shell/bazel/external_patching_test.sh
index 820b85963b..b9d6fd7b4f 100755
--- a/src/test/shell/bazel/external_patching_test.sh
+++ b/src/test/shell/bazel/external_patching_test.sh
@@ -493,4 +493,60 @@ EOF
   expect_not_log "BAD"
 }
 
+test_git_format_patch() {
+  EXTREPODIR=`pwd`
+
+  # Verify that a patch in the style of git-format-patch(1) can be handled.
+  mkdir main
+  cd main
+  ls -al
+  cat > 0001-foo.sh-remove-dragons.patch <<'EOF'
+From a8c0f9248dd85feac9d08b017776b5aedd1e7be8 Mon Sep 17 00:00:00 2001
+From: Klaus Aehlig <aehlig@google.com>
+Date: Wed, 13 Jun 2018 11:32:39 +0200
+Subject: [PATCH] foo.sh: remove dragons
+
+---
+ foo.sh | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/foo.sh b/foo.sh
+index 1f4c41e..9d548ff 100644
+--- a/foo.sh
++++ b/foo.sh
+@@ -1,3 +1,3 @@
+ #!/usr/bin/env sh
+
+-echo Here be dragons...
++echo New version of foo.sh, no more dangerous animals...
+--
+2.18.0.rc1.244.gcf134e6275-goog
+
+EOF
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+http_archive(
+  name="ext",
+  strip_prefix="ext-0.1.2",
+  urls=["file://${EXTREPODIR}/ext.zip"],
+  build_file_content="exports_files([\"foo.sh\"])",
+  patches = ["//:0001-foo.sh-remove-dragons.patch"],
+  patch_args = ["-p1"],
+  patch_cmds = ["find . -name '*.sh' -exec sed -i.orig '1s|#!/usr/bin/env sh\$|/bin/sh\$|' {} +"],
+)
+EOF
+  cat > BUILD <<'EOF'
+genrule(
+  name = "foo",
+  outs = ["foo.sh"],
+  srcs = ["@ext//:foo.sh"],
+  cmd = "cp $< $@; chmod u+x $@",
+  executable = True,
+)
+EOF
+  bazel build :foo.sh
+  foopath=`bazel info bazel-genfiles`/foo.sh
+  grep -q 'New version' $foopath || fail "expected patch to be applied"
+}
+
 run_suite "external patching tests"
diff --git a/tools/build_defs/repo/git.bzl b/tools/build_defs/repo/git.bzl
index 1ea5804d56..a46330542c 100644
--- a/tools/build_defs/repo/git.bzl
+++ b/tools/build_defs/repo/git.bzl
@@ -102,6 +102,7 @@ _common_attrs = {
     "strip_prefix": attr.string(default = ""),
     "patches": attr.label_list(default = []),
     "patch_tool": attr.string(default = "patch"),
+    "patch_args": attr.string_list(default = ["-p0"]),
     "patch_cmds": attr.string_list(default = []),
 }
 
@@ -161,6 +162,7 @@ Args:
   patches: A list of files that are to be applied as patches after extracting
     the archive.
   patch_tool: the patch(1) utility to use.
+  patch_args: arguments given to the patch tool, defaults to ["-p0"]
   patch_cmds: sequence of commands to be applied after patches are applied.
 """
 
@@ -196,5 +198,6 @@ Args:
   patches: A list of files that are to be applied as patches after extracting
     the archive.
   patch_tool: the patch(1) utility to use.
+  patch_args: arguments given to the patch tool, defaults to ["-p0"]
   patch_cmds: sequence of commands to be applied after patches are applied.
 """
diff --git a/tools/build_defs/repo/http.bzl b/tools/build_defs/repo/http.bzl
index 02879f4b7e..fffe226d7f 100644
--- a/tools/build_defs/repo/http.bzl
+++ b/tools/build_defs/repo/http.bzl
@@ -119,6 +119,7 @@ _http_archive_attrs = {
     "build_file_content": attr.string(),
     "patches": attr.label_list(default = []),
     "patch_tool": attr.string(default = "patch"),
+    "patch_args": attr.string_list(default = ["-p0"]),
     "patch_cmds": attr.string_list(default = []),
     "workspace_file": attr.label(),
     "workspace_file_content": attr.string(),
@@ -239,6 +240,7 @@ Args:
   patches: A list of files that are to be applied as patches after extracting
     the archive.
   patch_tool: the patch(1) utility to use.
+  patch_args: arguments given to the patch tool, defaults to ["-p0"]
   patch_cmds: sequence of commands to be applied after patches are applied.
 """
 
diff --git a/tools/build_defs/repo/utils.bzl b/tools/build_defs/repo/utils.bzl
index b76bac960e..4839b3e73b 100644
--- a/tools/build_defs/repo/utils.bzl
+++ b/tools/build_defs/repo/utils.bzl
@@ -66,9 +66,13 @@ def patch(ctx):
     """Implementation of patching an already extracted repository"""
     bash_exe = ctx.os.environ["BAZEL_SH"] if "BAZEL_SH" in ctx.os.environ else "bash"
     for patchfile in ctx.attr.patches:
-        command = "{patchtool} -p0 < {patchfile}".format(
+        command = "{patchtool} {patch_args} < {patchfile}".format(
             patchtool = ctx.attr.patch_tool,
             patchfile = ctx.path(patchfile),
+            patch_args = " ".join([
+                "'%s'" % arg
+                for arg in ctx.attr.patch_args
+            ]),
         )
         st = ctx.execute([bash_exe, "-c", command])
         if st.return_code: