Improve apt handling (#708)

* Unify apt/apt-get logic

The previous logic was buggy in that it tried to use `apt` in the `apt-get` branch after deciding that `apt` was unavailable...

* Prefer apt-get over apt

apt does not have a stable cli and using it from scripts yields annoying messages

* Improve English for missing apt-get & apt case

* Fix apt-get/apt fallback behavior for $ patterns

If there's a `$` in the apt install pattern, it will not fail if it selects a thing and decides it isn't interested in installing it.

* Fix spelling of libssl

src/Misc/layoutbin/installdependencies.sh

@@ -49,70 +49,68 @@ then
         cat /etc/debian_version
         echo "------------------------------"
         
-        # prefer apt over apt-get        
+        # prefer apt-get over apt
-        command -v apt
+        command -v apt-get
         if [ $? -eq 0 ]
         then
-            apt update && apt install -y liblttng-ust0 libkrb5-3 zlib1g
+            apt_get=apt-get
-            if [ $? -ne 0 ]
-            then
-                echo "'apt' failed with exit code '$?'"
-                print_errormessage
-                exit 1
-            fi
-
-            # libissl version prefer: libssl1.1 -> libssl1.0.2 -> libssl1.0.0
-            apt install -y libssl1.1$ || apt install -y libssl1.0.2$ || apt install -y libssl1.0.0$
-            if [ $? -ne 0 ]
-            then
-                echo "'apt' failed with exit code '$?'"
-                print_errormessage
-                exit 1
-            fi
-
-            # libicu version prefer: libicu66 -> libicu63 -> libicu60 -> libicu57 -> libicu55 -> libicu52
-            apt install -y libicu66 || apt install -y libicu63 || apt install -y libicu60 || apt install -y libicu57 || apt install -y libicu55 || apt install -y libicu52
-            if [ $? -ne 0 ]
-            then
-                echo "'apt' failed with exit code '$?'"
-                print_errormessage
-                exit 1
-            fi
         else
-            command -v apt-get
+            command -v apt
             if [ $? -eq 0 ]
             then
-                apt-get update && apt-get install -y liblttng-ust0 libkrb5-3 zlib1g
+                apt_get=apt
-                if [ $? -ne 0 ]
-                then
-                    echo "'apt-get' failed with exit code '$?'"
-                    print_errormessage
-                    exit 1
-                fi
-                
-                # libissl version prefer: libssl1.1 -> libssl1.0.2 -> libssl1.0.0
-                apt-get install -y libssl1.1$ || apt-get install -y libssl1.0.2$ || apt install -y libssl1.0.0$
-                if [ $? -ne 0 ]
-                then
-                    echo "'apt-get' failed with exit code '$?'"
-                    print_errormessage
-                    exit 1
-                fi
-
-                # libicu version prefer: libicu66 -> libicu63 -> libicu60 -> libicu57 -> libicu55 -> libicu52
-                apt-get install -y libicu66 || apt-get install -y libicu63 || apt-get install -y libicu60 || apt install -y libicu57 || apt install -y libicu55 || apt install -y libicu52
-                if [ $? -ne 0 ]
-                then
-                    echo "'apt-get' failed with exit code '$?'"
-                    print_errormessage
-                    exit 1
-                fi
             else
-                echo "Can not find 'apt' or 'apt-get'"
+                echo "Found neither 'apt-get' nor 'apt'"
                 print_errormessage
                 exit 1
             fi
         fi
+
+        $apt_get update && $apt_get install -y liblttng-ust0 libkrb5-3 zlib1g
+        if [ $? -ne 0 ]
+        then
+            echo "'$apt_get' failed with exit code '$?'"
+            print_errormessage
+            exit 1
+        fi
+
+        apt_get_with_fallbacks() {
+            $apt_get install -y $1
+            fail=$?
+            if [ $fail -eq 0 ]
+            then
+                if [ "${1#"${1%?}"}" = '$' ]; then
+                    dpkg -l "${1%?}" > /dev/null 2> /dev/null
+                    fail=$?
+                fi
+            fi
+            if [ $fail -ne 0 ]
+            then
+                shift
+                if [ -n "$1" ]
+                then
+                    apt_get_with_fallbacks "$@"
+                fi
+            fi
+        }
+
+        # libssl version prefer: libssl1.1 -> libssl1.0.2 -> libssl1.0.0
+        apt_get_with_fallbacks libssl1.1$ libssl1.0.2$ libssl1.0.0$
+        if [ $? -ne 0 ]
+        then
+            echo "'$apt_get' failed with exit code '$?'"
+            print_errormessage
+            exit 1
+        fi
+
+        # libicu version prefer: libicu66 -> libicu63 -> libicu60 -> libicu57 -> libicu55 -> libicu52
+        apt_get_with_fallbacks libicu66 libicu63 libicu60 libicu57 libicu55 libicu52
+        if [ $? -ne 0 ]
+        then
+            echo "'$apt_get' failed with exit code '$?'"
+            print_errormessage
+            exit 1
+        fi
     elif [ -e /etc/redhat-release ]
     then
         echo "The current OS is Fedora based"