[Bug 1679789] [NEW] Trailing slash missing from Dir::Cache in apt configuration

[jimav]

Public bug reported:

The apt configuration database has some incompatible changes which break
existing scripts.  It is not obvious that this was deliberate (I hope
not).

Prior to 16.10, the configured cache directory path(s) included a
trailing slash.  Now they do not include the trailing slash.  This
breaks existing scripts which combine bits from the configuration
database.

In 16.04:
  $ apt-config shell D Dir C Dir::Cache F Dir::Cache::pkgcache
  D='/'
  C='var/cache/apt/'
  F='pkgcache.bin'

  So if this output is eval'd in the shell, then
     path=${D}${C}${F}  produces "/var/cache/apt/pkgcache.bin"

However in 16.10:
  $ apt-config shell D Dir C Dir::Cache F Dir::Cache::pkgcache
  D='/'
  C='var/cache/apt'
  F='pkgcache.bin'

  So existing shell code now breaks
    path=${D}${C}${F}  produces "/var/cache/aptpkgcache.bin"

If this was a mistake, please fix ASAP.  
If it was on purpose, please post (a link to) an explanation.

Thanks.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: apt 1.3.4
ProcVersionSignature: Ubuntu 4.8.0-46.49-generic 4.8.17
Uname: Linux 4.8.0-46-generic x86_64
ApportVersion: 2.20.3-0ubuntu8.2
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Apr  4 10:33:13 2017
InstallationDate: Installed on 2016-05-06 (332 days ago)
InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Alpha amd64 (20160506)
SourcePackage: apt
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: apt (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug yakkety

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https://bugs.launchpad.net/bugs/1679789

Title:
  Trailing slash missing from Dir::Cache in apt configuration

Status in apt package in Ubuntu:
  New

Bug description:
  The apt configuration database has some incompatible changes which
  break existing scripts.  It is not obvious that this was deliberate (I
  hope not).

  Prior to 16.10, the configured cache directory path(s) included a
  trailing slash.  Now they do not include the trailing slash.  This
  breaks existing scripts which combine bits from the configuration
  database.

  In 16.04:
    $ apt-config shell D Dir C Dir::Cache F Dir::Cache::pkgcache
    D='/'
    C='var/cache/apt/'
    F='pkgcache.bin'

    So if this output is eval'd in the shell, then
       path=${D}${C}${F}  produces "/var/cache/apt/pkgcache.bin"

  However in 16.10:
    $ apt-config shell D Dir C Dir::Cache F Dir::Cache::pkgcache
    D='/'
    C='var/cache/apt'
    F='pkgcache.bin'

    So existing shell code now breaks
      path=${D}${C}${F}  produces "/var/cache/aptpkgcache.bin"

  If this was a mistake, please fix ASAP.  
  If it was on purpose, please post (a link to) an explanation.

  Thanks.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: apt 1.3.4
  ProcVersionSignature: Ubuntu 4.8.0-46.49-generic 4.8.17
  Uname: Linux 4.8.0-46-generic x86_64
  ApportVersion: 2.20.3-0ubuntu8.2
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Tue Apr  4 10:33:13 2017
  InstallationDate: Installed on 2016-05-06 (332 days ago)
  InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Alpha amd64 (20160506)
  SourcePackage: apt
  UpgradeStatus: No upgrade log present (probably fresh install)

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