Add --mtime flag to build_tar.py. Use this feature for pkg_tar.

This effectively reverts part of #7276.
archive.py no longer makes TAR files with the mtime 2000-01-01.
Now, only tar files made with the pkg_tar() rule will get that mtime value by default.
This means other users of archive.py (e.g. rules_docker) will not experience a sudden change in tar content when updating Bazel.

#1299

@beasleyr-vmw: Can you test this in your process to see that it still solves issue 1299 for you?

Closes #7482.

PiperOrigin-RevId: 234991284

tools/build_defs/pkg/README.md

@@ -173,6 +173,25 @@ Creates a tar file from a list of inputs.
         </p>
       </td>
     </tr>
+    <tr>
+      <td><code>mtime</code></td>
+      <td>
+        <code>int, seconds since Jan 1, 1970, default to -1 (ignored)</code>
+        <p>
+          Set the mod time of files added by the <code>files</code> attribute.
+        </p>
+      </td>
+    </tr>
+    <tr>
+      <td><code>portale_mtime</code></td>
+      <td>
+        <code>bool, default True</code>
+        <p>
+          Set the mod time of files added by the <code>files</code> attribute
+          to a 2000-01-01.
+        </p>
+      </td>
+    </tr>
     <tr>
       <td><code>modes</code></td>
       <td>

tools/build_defs/pkg/archive.py

@@ -22,7 +22,7 @@
 
 # Use a deterministic mtime that doesn't confuse other programs.
 # See: https://github.com/bazelbuild/bazel/issues/1299
-MTIME = 946684800  # 2000-01-01 00:00:00.000 UTC
+PORTABLE_MTIME = 946684800  # 2000-01-01 00:00:00.000 UTC
 
 
 class SimpleArFile(object):
@@ -110,14 +110,16 @@ def __init__(self,
                name,
                compression='',
                root_directory='./',
-               default_mtime=MTIME):
+               default_mtime=None):
     """TarFileWriter wraps tarfile.open().
 
     Args:
       name: the tar file name.
       compression: compression type: bzip2, bz2, gz, tgz, xz, lzma.
       root_directory: virtual root to prepend to elements in the archive.
       default_mtime: default mtime to use for elements in the archive.
+          May be an integer or the value 'portable' to use the date
+          2000-01-01, which is compatible with non *nix OSes'.
     """
     if compression in ['bzip2', 'bz2']:
       mode = 'w:bz2'
@@ -128,7 +130,12 @@ def __init__(self,
     self.xz = compression in ['xz', 'lzma']
     self.name = name
     self.root_directory = root_directory.rstrip('/')
-    self.default_mtime = default_mtime
+    if default_mtime is None:
+      self.default_mtime = 0
+    elif default_mtime == 'portable':
+      self.default_mtime = PORTABLE_MTIME
+    else:
+      self.default_mtime = int(default_mtime)
 
     self.fileobj = None
     if self.gz:
@@ -292,8 +299,6 @@ def add_file(self,
       tarinfo.mode = 0o644 if kind == tarfile.REGTYPE else 0o755
     else:
       tarinfo.mode = mode
-    if mtime < 0:
-      mtime = self.default_mtime
     if link:
       tarinfo.linkname = link
     if content:

tools/build_defs/pkg/build_tar.py

@@ -34,6 +34,11 @@
 gflags.DEFINE_string('mode', None,
                      'Force the mode on the added files (in octal).')
 
+gflags.DEFINE_string(
+    'mtime', None, 'Set mtime on tar file entries. May be an integer or the'
+    ' value "portable", to get the value 2000-01-01, which is'
+    ' is usable with non *nix OSes')
+
 gflags.DEFINE_multistring('empty_file', [], 'An empty file to add to the layer')
 
 gflags.DEFINE_multistring('empty_dir', [], 'An empty dir to add to the layer')
@@ -86,20 +91,25 @@
 
 
 class TarFile(object):
-  """A class to generates a Docker layer."""
+  """A class to generates a TAR file."""
 
   class DebError(Exception):
     pass
 
-  def __init__(self, output, directory, compression, root_directory):
+  def __init__(self, output, directory, compression, root_directory,
+               default_mtime):
     self.directory = directory
     self.output = output
     self.compression = compression
     self.root_directory = root_directory
+    self.default_mtime = default_mtime
 
   def __enter__(self):
-    self.tarfile = archive.TarFileWriter(self.output, self.compression,
-                                         self.root_directory)
+    self.tarfile = archive.TarFileWriter(
+        self.output,
+        self.compression,
+        self.root_directory,
+        default_mtime=self.default_mtime)
     return self
 
   def __exit__(self, t, v, traceback):
@@ -326,7 +336,7 @@ def main(unused_argv):
 
   # Add objects to the tar file
   with TarFile(FLAGS.output, FLAGS.directory, FLAGS.compression,
-               FLAGS.root_directory) as output:
+               FLAGS.root_directory, FLAGS.mtime) as output:
 
     def file_attributes(filename):
       if filename.startswith('/'):

tools/build_defs/pkg/pkg.bzl

@@ -47,6 +47,12 @@ def _pkg_tar_impl(ctx):
         "--owner=" + ctx.attr.owner,
         "--owner_name=" + ctx.attr.ownername,
     ]
+    if ctx.attr.mtime != -1:  # Note: Must match default in rule def.
+        if ctx.attr.portable_mtime:
+            fail("You may not set both mtime and portable_mtime")
+        args.append("--mtime=" + ctx.attr.mtime)
+    if ctx.attr.portable_mtime:
+        args.append("--mtime=portable")
 
     # Add runfiles if requested
     file_inputs = []
@@ -218,6 +224,8 @@ _real_pkg_tar = rule(
         "files": attr.label_keyed_string_dict(allow_files = True),
         "mode": attr.string(default = "0555"),
         "modes": attr.string_dict(),
+        "mtime": attr.int(default = -1),
+        "portable_mtime": attr.bool(default = True),
         "owner": attr.string(default = "0.0"),
         "ownername": attr.string(default = "."),
         "owners": attr.string_dict(),