Merge ubiquity:usr-merge into ubiquity:master

[Dimitri John Ledkov]

Support usr-merge in ubiquity.

With introduction of usr-merge in disco, we started to have top-level symlinks to dirs i.e. /sbin -> /usr/sbin which broke with blacklisting logic. Because such a symlink may not be blacklisted, even though blacklisted packages ship /sbin directory. A simple check if that is a dir is no longer sufficient. Instead extended the blacklisting logic to prevent blacklisting symlinks to dirs.

LP: #1801408

[Dimitri John Ledkov (xnox)]

Hm, maybe i went overboard with this checks, since top-level things must be dirs or symlinks to dirs, thus `and '/' in relpath` would actually be sufficient.

Unmerged commits

bc3a7d8... by Dimitri John Ledkov on 2018-11-06

Support usr-merge in ubiquity.

With introduction of usr-merge in disco, we started to have top-level
symlinks to dirs i.e. /sbin -> /usr/sbin which broke with blacklisting
logic. Because such a symlink may not be blacklisted, even though
blacklisted packages ship /sbin directory. A simple check if that is a
dir is no longer sufficient. Instead extended the blacklisting logic
to prevent blacklisting symlinks to dirs.

LP: #1801408

diff --git a/debian/changelog b/debian/changelog
index 226963a..a9dcce5 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -3,6 +3,7 @@ ubiquity (19.04.1) UNRELEASED; urgency=medium
   * Update d-i sources to point at disco
   * Automatic update of included source packages: choose-mirror
     2.78ubuntu5, preseed 1.71ubuntu9.
+  * Support usr-merge in ubiquity. LP: #1801408
 
  -- Dimitri John Ledkov <[e-mail]>  Tue, 06 Nov 2018 13:25:41 +0000
 
diff --git a/scripts/install.py b/scripts/install.py
index fb89ceb..69a0c9d 100755
--- a/scripts/install.py
+++ b/scripts/install.py
@@ -436,9 +436,30 @@ class Install(install_misc.InstallBase):
                 targetpath = os.path.join(self.target, relpath)
                 st = os.lstat(sourcepath)
 
+                def blacklisted(st, sourcepath, relpath):
+                    # Not blacklisted, we are done
+                    if '/%s' % relpath not in self.blacklist:
+                        return False
+                    # If a path is blacklisted, it gets tricky
+                    # Directories are not blacklistable
+                    if stat.S_ISDIR(st.st_mode):
+                        return False
+                    # Everything else is... but symlinks are special
+                    if not stat.S_ISLNK(st.st_mode):
+                        return True
+                    # Does it exist?!
+                    if not os.path.exists(os.path.realpath(sourcepath)):
+                        return True
+                    # mostly blacklistable, unless they point to a dir
+                    if not stat.S_ISDIR(os.stat(sourcepath).st_mode):
+                        return True
+                    # thus final condition
+                    # top-level symlink to a dir is not blacklistable
+                    # ie. /sbin -> /usr/sbin
+                    return '/' in relpath
+
                 # Is the path blacklisted?
-                if (not stat.S_ISDIR(st.st_mode) and
-                        '/%s' % relpath in self.blacklist):
+                if blacklisted(st, sourcepath, relpath):
                     if debug:
                         syslog.syslog('Not copying %s' % relpath)
                     continue