Add support for Phased-Update-Percentage

This adds support for Phased-Update-Percentage by pinning
upgrades that are not to be installed down to 1.

The output of policy has been changed to add the level of
phasing, and documentation has been improved to document
how phased updates work.

The patch detects if it is running in a chroot, and if so, always
includes phased updates, restoring classic apt behavior to avoid
behavioral changes on buildd chroots.

Various options are added to control this all:

* APT::Get::{Always,Never}-Include-Phased-Updates and their legacy
  update-manager equivalents to always or never include phased updates
* APT::Machine-ID can be set to a UUID string to have all machines in a
  fleet phase the same
* Dir::Etc::Machine-ID is weird in that it's default is sort of like
  ../machine-id, but not really, as ../machine-id would look up
  $PWD/../machine-id and not relative to Dir::Etc; but it allows you to
  override the path to machine-id (as opposed to the value)
* Dir::Bin::ischroot is the path to the ischroot(1) binary which is used
  to detect whether we are running in a chroot.

1 files changed, 14 insertions, 0 deletions

diff --git a/apt-pkg/cacheiterators.h b/apt-pkg/cacheiterators.h
index 1b049b6e5..6261b5089 100644
--- a/apt-pkg/cacheiterators.h
+++ b/apt-pkg/cacheiterators.h
@@ -242,6 +242,20 @@ class APT_PUBLIC pkgCache::VerIterator : public Iterator<Version, VerIterator> {
 	bool Automatic() const;
 	VerFileIterator NewestFile() const;
 
+#ifdef APT_COMPILING_APT
+	inline unsigned int PhasedUpdatePercentage() const
+	{
+	   return (static_cast<Version::Extra *>(Owner->Map.Data()) + S->d)->PhasedUpdatePercentage;
+	}
+	inline bool PhasedUpdatePercentage(unsigned int percentage)
+	{
+	   if (percentage > 100)
+	      return false;
+	   (static_cast<Version::Extra *>(Owner->Map.Data()) + S->d)->PhasedUpdatePercentage = static_cast<uint8_t>(percentage);
+	   return true;
+	}
+#endif
+
 	inline VerIterator(pkgCache &Owner,Version *Trg = 0) : Iterator<Version, VerIterator>(Owner, Trg) {
 		if (S == 0)
 			S = OwnerPointer();