Fix regression with distutils MANIFEST handing (#11104, #8688).

The changed behavior of sdist in 3.1 broke packaging for projects that
wanted to use a manually-maintained MANIFEST file (instead of having a
MANIFEST.in template and letting distutils generate the MANIFEST).

The fixes that were committed for #8688 (76643c286b9f by Tarek and
d54da9248ed9 by me) did not fix all issues exposed in the bug report,
and also added one problem: the MANIFEST file format gained comments,
but the read_manifest method was not updated to handle (i.e. ignore)
them.  This changeset should fix everything; the tests have been
expanded and I successfully tested the 2.7 version with Mercurial, which
suffered from this regression.

I have grouped the versionchanged directives for these bugs in one place
and added micro version numbers to help users know the quirks of the
exact version they’re using.

Initial report, thorough diagnosis and patch by John Dennis, further
work on the patch by Stephen Thorne, and a few edits and additions by
me.

1 files changed, 17 insertions, 8 deletions

diff --git a/Doc/distutils/sourcedist.rst b/Doc/distutils/sourcedist.rst
index 15d0baf..1666436 100644
--- a/Doc/distutils/sourcedist.rst
+++ b/Doc/distutils/sourcedist.rst
@@ -103,10 +103,20 @@ per line, regular files (or symlinks to them) only.  If you do supply your own
 :file:`MANIFEST`, you must specify everything: the default set of files
 described above does not apply in this case.
 
-.. versionadded:: 3.1
+.. versionchanged:: 3.1
+   An existing generated :file:`MANIFEST` will be regenerated without
+   :command:`sdist` comparing its modification time to the one of
+   :file:`MANIFEST.in` or :file:`setup.py`.
+
+.. versionchanged:: 3.1.3
    :file:`MANIFEST` files start with a comment indicating they are generated.
    Files without this comment are not overwritten or removed.
 
+.. versionchanged:: 3.2.2
+   :command:`sdist` will read a :file:`MANIFEST` file if no :file:`MANIFEST.in`
+   exists, like it used to do.
+
+
 The manifest template has one command per line, where each command specifies a
 set of files to include or exclude from the source distribution.  For an
 example, again we turn to the Distutils' own manifest template::
@@ -185,8 +195,12 @@ Manifest-related options
 
 The normal course of operations for the :command:`sdist` command is as follows:
 
-* if the manifest file, :file:`MANIFEST` doesn't exist, read :file:`MANIFEST.in`
-  and create the manifest
+* if the manifest file (:file:`MANIFEST` by default) exists and the first line
+  does not have a comment indicating it is generated from :file:`MANIFEST.in`,
+  then it is used as is, unaltered
+
+* if the manifest file doesn't exist or has been previously automatically
+  generated, read :file:`MANIFEST.in` and create the manifest
 
 * if neither :file:`MANIFEST` nor :file:`MANIFEST.in` exist, create a manifest
   with just the default file set
@@ -204,8 +218,3 @@ distribution::
    python setup.py sdist --manifest-only
 
 :option:`-o` is a shortcut for :option:`--manifest-only`.
-
-.. versionchanged:: 3.1
-   An existing generated :file:`MANIFEST` will be regenerated without
-   :command:`sdist` comparing its modification time to the one of
-   :file:`MANIFEST.in` or :file:`setup.py`.