Added gsutil/gslib to depot_tools/third_party

third_party/gsutil/gslib/addlhelp/metadata.py

Index: third_party/gsutil/gslib/addlhelp/metadata.py
diff --git a/third_party/gsutil/gslib/addlhelp/metadata.py b/third_party/gsutil/gslib/addlhelp/metadata.py
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+# Copyright 2012 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from gslib.help_provider import HELP_NAME
+from gslib.help_provider import HELP_NAME_ALIASES
+from gslib.help_provider import HELP_ONE_LINE_SUMMARY
+from gslib.help_provider import HelpProvider
+from gslib.help_provider import HELP_TEXT
+from gslib.help_provider import HelpType
+from gslib.help_provider import HELP_TYPE
+
+_detailed_help_text = ("""
+<B>OVERVIEW OF METADATA</B>
+  Objects can have associated metadata, which control aspects of how
+  GET requests are handled, including Content-Type, Cache-Control,
+  Content-Disposition, and Content-Encoding (discussed in more detail in
+  the subsections below). In addition, you can set custom metadata that
+  can be used by applications (e.g., tagging that particular objects possess
+  some property).
+
+  There are two ways to set metadata on objects:
+
+    - at upload time you can specify one or more headers to associate with
+      objects, using the gsutil -h option.  For example, the following command
+      would cause gsutil to set the Content-Type and Cache-Control for each
+      of the files being uploaded:
+
+        gsutil -h "Content-Type:text/html" -h "Cache-Control:public, max-age=3600" cp -r images gs://bucket/images
+
+      Note that -h is an option on the gsutil command, not the cp sub-command.
+
+    - You can set or remove metadata fields from already uploaded objects using
+      the gsutil setmeta command. See "gsutil help setmeta".
+
+  More details about specific pieces of metadata are discussed below.
+
+
+<B>CONTENT TYPE</B>
+  The most commonly set metadata is Content-Type (also known as MIME type),
+  which allows browsers to render the object properly. 
+  gsutil sets the Content-Type
+  automatically at upload time, based on each filename extension. For
+  example, uploading files with names ending in .txt will set Content-Type
+  to text/plain. If you're running gsutil on Linux or MacOS and would prefer
+  to have content type set based on naming plus content examination, see the
+  use_magicfile configuration variable in the gsutil/boto configuration file
+  (See also "gsutil help config"). In general, using use_magicfile is more
+  robust and configurable, but is not available on Windows.
+
+  If you specify a -h header when uploading content (like the example gsutil
+  command given in the previous section), it overrides the Content-Type that
+  would have been set based on filename extension or content.  This can be
+  useful if the Content-Type detection algorithm doesn't work as desired
+  for some of your files.
+
+  You can also completely suppress content type detection in gsutil, by
+  specifying an empty string on the Content-Type header:
+
+    gsutil -h 'Content-Type:' cp -r images gs://bucket/images
+
+  In this case, the Google Cloud Storage service will attempt to detect
+  the content type. In general this approach will work better than using
+  filename extension-based content detection in gsutil, because the list of
+  filename extensions is kept more current in the server-side content detection
+  system than in the Python library upon which gsutil content type detection
+  depends. (For example, at the time of writing this, the filename extension
+  ".webp" was recognized by the server-side content detection system, but
+  not by gsutil.)
+
+
+<B>CACHE-CONTROL</B>
+  Another commonly set piece of metadata is Cache-Control, which allows
+  you to control whether and for how long browser and Internet caches are
+  allowed to cache your objects. Cache-Control only applies to objects with
+  a public-read ACL. Non-public data are not cacheable.
+
+  Here's an example of uploading an object set to allow caching:
+
+    gsutil -h "Cache-Control:public,max-age=3600" cp -a public-read -r html gs://bucket/html
+
+  This command would upload all files in the html directory (and subdirectories)
+  and make them publicly readable and cacheable, with cache expiration of
+  one hour.
+
+  Note that if you allow caching, at download time you may see older versions
+  of objects after uploading a newer replacement object. Note also that because
+  objects can be cached at various places on the Internet there is no way to
+  force a cached object to expire globally (unlike the way you can force your
+  browser to refresh its cache).
+
+
+<B>CONTENT-ENCODING</B>
+  You could specify Content-Encoding to indicate that an object is compressed,
+  using a command like:
+
+    gsutil -h "Content-Encoding:gzip" cp *.gz gs://bucket/compressed
+
+  Note that Google Cloud Storage does not compress or decompress objects. If
+  you use this header to specify a compression type or compression algorithm
+  (for example, deflate), Google Cloud Storage preserves the header but does
+  not compress or decompress the object.  Instead, you need to ensure that
+  the files have been compressed using the specified Content-Encoding before
+  using gsutil to upload them.
+
+  For compressible content, using Content-Encoding:gzip saves network and
+  storage costs, and improves content serving performance (since most browsers
+  are able to decompress objects served this way).
+
+  Note also that gsutil provides an easy way to cause content to be compressed
+  and stored with Content-Encoding:gzip: see the -z option in "gsutil help cp".
+
+
+<B>CONTENT-DISPOSITION</B>
+  You can set Content-Disposition on your objects, to specify presentation
+  information about the data being transmitted. Here's an example:
+
+    gsutil -h 'Content-Disposition:attachment; filename=filename.ext' \\
+      cp -r attachments gs://bucket/attachments
+
+  Setting the Content-Disposition allows you to control presentation style
+  of the content, for example determining whether an attachment should be
+  automatically displayed vs should require some form of action from the user to
+  open it.  See http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.5.1
+  for more details about the meaning of Content-Disposition.
+
+
+<B>CUSTOM METADATA</B>
+  You can add your own custom metadata (e.g,. for use by your application)
+  to an object by setting a header that starts with "x-goog-meta", for example:
+
+    gsutil -h x-goog-meta-reviewer:jane cp mycode.java gs://bucket/reviews
+
+  You can add multiple differently named custom metadata fields to each object.
+
+
+<B>SETTABLE FIELDS; FIELD VALUES</B>
+  You can't set some metadata fields, such as ETag and Content-Length. The
+  fields you can set are:
+    - Cache-Control
+    - Content-Disposition
+    - Content-Encoding
+    - Content-Language
+    - Content-MD5
+    - Content-Type
+    - Any field starting with X-GOOG-META- (i.e., custom metadata).
+
+  Header names are case-insensitive.
+
+  X-GOOG-META- fields can have data set to arbitrary Unicode values. All
+  other fields must have ASCII values.
+
+
+<B>VIEWING CURRENTLY SET METADATA</B>
+  You can see what metadata is currently set on an object by using:
+
+    gsutil ls -L gs://the_bucket/the_object
+""")
+
+
+class CommandOptions(HelpProvider):
+  """Additional help about object metadata."""
+
+  help_spec = {
+    # Name of command or auxiliary help info for which this help applies.
+    HELP_NAME : 'metadata',
+    # List of help name aliases.
+    HELP_NAME_ALIASES : ['cache-control', 'caching', 'content type',
+                         'mime type', 'mime', 'type'],
+    # Type of help:
+    HELP_TYPE : HelpType.ADDITIONAL_HELP,
+    # One line summary of this help.
+    HELP_ONE_LINE_SUMMARY : 'Working with object metadata',
+    # The full help text.
+    HELP_TEXT : _detailed_help_text,
+  }