pkg_digger: remove -i option, add -s option for sorted output.

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Default answer Yes to all questions.
nih -n -- answer no to all questions.

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Update nih.

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Keep MESSAGES in special file and tell user about it.

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Variables NIH-{command} with options always applied, e.g.
 NIH_list=-q or NIH_list=-i. This will make special variables
 for install -l|-L and -p|-P obsolete.

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always "nih verify" before "nih uninstal/install"

nih deps should accept pkgbase or pkgname or pkgpaba but output what
is requested

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# nih update curl-7.33.0
Generating an update plan...
    R:1 U:1 A:0
Update plan cannot be built
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The above problem is caused by the following
   u: unicity curl <- www/curl www/curl
curl-7.32.0 --> curl-7.33.0

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nih update _
   The above problem is caused by the following
      d: not_found jpeg>=9 <- graphics/py-imaging py27-imaging-1.1.7nb7
   py27-imaging-1.1.7nb4 --> py27-imaging-1.1.7nb7

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nih search -- sort found packages alphabetically

nih status -- pkgin-like output

-k marked packages are not installed => problems with PROVIDES/REQUIRES

nih verify -s vs. 6.0_STABLE/6.0_RELEASE
nih install -N - do not alter auto-installed flag

to fix: "Checking packages from update plan for common files..."
  tries to find packages in current directory even if
  package was installed using full path.

plan -1:
- nih uninstall: do not require .nih/pkg_summary.txt (ano)
- nih install -u mark as installed -a autoinstalled
- fix for -L
- multiple pkg_summary(5) (e.g. 5.0-indep)

plan0:
- use distbb for source-based update

plan1:
- nih status: -v analyse vulnerable packages against binary or pkgsrc tree
- nih install: ability to check a number bytes to download and
  install/remove
- nih status: -N   -- check installed(?) packages
                      against build-time dependencies
- nih clean-distdir

- Use pkg_summary-YYYYMMDD.txt
  in 'nih clean-cache' and 'nih install'
- before update warn about missed binaries for installed packages
  (downgrade will not be possible)

plan2:
- nih remove/install: syslog (idea belongs to Marc Espie)
- nih install: a way to download ALL packages at once
  using different mirrors (for those who have very fast internet connection).
- nih status: -S   -- analyse symbols?
- nih clean-cache:    use FILE_NAME
- autoverifying pkgdb after installation
- separate pkg_install_plan script from nih
- {sha512,pkg_summary} -> {sha512,pkg_summary}_YYYYMMDD only if they differ
- pkg_refresh_summary needs to be speeded-up
