[libcalamares] Fix up smart-string-truncation

- off-by-one when source ends with a newline
- lastNewLine was being calculated as a left-index into the string,
  then used as a count-from-right

src/libcalamares/utils/String.cpp

@@ -15,6 +15,7 @@
  */
 
 #include "String.h"
+#include "Logger.h"
 
 #include <QStringList>
 
@@ -138,7 +139,7 @@ truncateMultiLine( const QString& string, CalamaresUtils::LinesStartEnd lines, C
         return string;
     }
 
-    QString shorter = string.simplified();
+    QString shorter = string;
     QString front, back;
     if ( shorter.count( '\n' ) >= maxLines )
     {
@@ -154,17 +155,17 @@ truncateMultiLine( const QString& string, CalamaresUtils::LinesStartEnd lines, C
         }
         if ( from > 0 )
         {
-            front = shorter.left( from );
+            front = shorter.left( from + 1 );
         }
 
         int lastNewLine = -1;
-        int lastCount = 0;
+        int lastCount = shorter.endsWith( '\n' ) ? -1 : 0;
         for ( auto i = shorter.rbegin(); i != shorter.rend() && lastCount < lines.atEnd; ++i )
         {
             if ( *i == '\n' )
             {
                 ++lastCount;
-                lastNewLine = shorter.length() - int( i - shorter.rbegin() );
+                lastNewLine = int( i - shorter.rbegin() );
             }
         }
         if ( ( lastNewLine >= 0 ) && ( lastCount >= lines.atEnd ) )

src/libcalamares/utils/Tests.cpp

@@ -501,6 +501,8 @@ strings: [ aap, noot, mies ]
 void
 LibCalamaresTests::testStringTruncation()
 {
+    Logger::setupLogLevel( Logger::LOGDEBUG );
+
     using namespace CalamaresUtils;
 
     const QString longString( R"(---
@@ -546,14 +548,18 @@ LibCalamaresTests::testStringTruncation()
     // Lines at the start
     {
         auto s = truncateMultiLine( longString, LinesStartEnd { 4, 0 }, CharCount { sufficientLength } );
+        QVERIFY( s.length() > 1 );
         QVERIFY( longString.startsWith( s ) );
+        cDebug() << "Result-line" << Logger::Quote << s;
         QCOMPARE( s.count( '\n' ), 4 );
     }
 
     // Lines at the end
     {
         auto s = truncateMultiLine( longString, LinesStartEnd { 0, 4 }, CharCount { sufficientLength } );
+        QVERIFY( s.length() > 1 );
         QVERIFY( longString.endsWith( s ) );
+        cDebug() << "Result-line" << Logger::Quote << s;
         QCOMPARE( s.count( '\n' ), 4 );
     }
 }