apt-*: add more info links; apt-file: add regex search example (#5710)

pages/linux/apt-add-repository.md

@@ -1,6 +1,7 @@
 # apt-add-repository
 
 > Manages apt repository definitions.
+> More information: <https://manpages.debian.org/latest/software-properties-common/apt-add-repository.1.html>.
 
 - Add a new apt repository:
 

pages/linux/apt-cache.md

@@ -1,6 +1,7 @@
 # apt-cache
 
 > Debian and Ubuntu package query tool.
+> More information: <https://manpages.debian.org/latest/apt/apt-cache.8.html>.
 
 - Search for a package in your current sources:
 

pages/linux/apt-file.md

@@ -1,6 +1,7 @@
 # apt-file
 
 > Search for files in apt packages, including ones not yet installed.
+> More information: <https://manpages.debian.org/latest/apt-file/apt-file.1.html>.
 
 - Update the metadata database:
 
@@ -8,8 +9,12 @@
 
 - Search for packages that contain the specified file or path:
 
-`apt-file search {{part/of/filename}}`
+`apt-file {{search|find}} {{part/of/filename}}`
 
 - List the contents of a specific package:
 
-`apt-file list {{package_name}}`
+`apt-file {{show|list}} {{package_name}}`
+
+- Search for packages that match the regular expresssion given in `pattern`:
+
+`apt-file {{search|find}} --regexp {{pattern}}`

pages/linux/apt-get.md

@@ -2,6 +2,7 @@
 
 > Debian and Ubuntu package management utility.
 > Search for packages using `apt-cache`.
+> More information: <https://manpages.debian.org/latest/apt/apt-get.8.html>.
 
 - Update the list of available packages and versions (it's recommended to run this before other `apt-get` commands):
 

pages/linux/apt-key.md

@@ -1,6 +1,8 @@
 # apt-key
 
 > Key management utility for the APT Package Manager on Debian and Ubuntu.
+> Note: `apt-key` is now deprecated (except for the use of `apt-key del` in maintainer scripts).
+> More information: <https://manpages.debian.org/latest/apt/apt-key.8.html>.
 
 - List trusted keys:
 

pages/linux/apt-mark.md

@@ -1,6 +1,7 @@
 # apt-mark
 
 > Utility to change the status of installed packages.
+> More information: <https://manpages.debian.org/latest/apt/apt-mark.8.html>.
 
 - Mark a package as automatically installed:
 

pages/linux/apt.md

@@ -2,6 +2,7 @@
 
 > Package management utility for Debian based distributions.
 > Recommended replacement for apt-get when used interactively in Ubuntu versions 16.04 and later.
+> More information: <https://manpages.debian.org/latest/apt/apt.8.html>.
 
 - Update the list of available packages and versions (it's recommended to run this before other `apt` commands):
 

pages/linux/aptitude.md

@@ -1,6 +1,7 @@
 # aptitude
 
 > Debian and Ubuntu package management utility.
+> More information: <https://manpages.debian.org/latest/aptitude/aptitude.8.html>.
 
 - Synchronize list of packages and versions available. This should be run first, before running subsequent aptitude commands:
 

pages/linux/netselect-apt.md

@@ -1,7 +1,7 @@
 # netselect-apt
 
 > Create a `sources.list` file for a Debian mirror with the lowest latency.
-> More information: <https://manpages.debian.org/buster/netselect-apt/netselect-apt.1.en.html>.
+> More information: <https://manpages.debian.org/buster/netselect-apt/netselect-apt.1.html>.
 
 - Create `sources.list` using the lowest latency server: