Extend documentation for QFile:copy()

- Add information about symlinks and file metadata.
- Reflow text.
- Extract text common to both overloads to a .qdocinc file
  for consistency and to avoid duplication.

Fixes: QTBUG-94706
Change-Id: I3c730fd63f4018a1a573bb56751fedd2270a3247
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit cc2fdce35e6a958e021b4d4cdc0ace1a91b06d0c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/doc/src/includes/qfile-copy.qdocinc

@@ -0,0 +1,11 @@
+This file is closed before it is copied.
+
+If the copied file is a symbolic link (symlink), the
+file it refers to is copied, not the link itself. With the
+exception of permissions, which are copied, no other file metadata
+is copied.
+
+Returns \c true if successful; otherwise returns \c false.
+
+Note that if a file with the name \a newName already exists,
+copy() returns \c false. This means QFile will not overwrite it.

src/corelib/io/qfile.cpp

@@ -755,13 +755,9 @@ QFile::link(const QString &fileName, const QString &linkName)
 }
 
 /*!
-    Copies the file currently specified by fileName() to a file called
+    Copies the file named fileName() to \a newName.
-    \a newName.  Returns \c true if successful; otherwise returns \c false.
 
-    Note that if a file with the name \a newName already exists,
+    \include qfile-copy.qdocinc
-    copy() returns \c false (i.e. QFile will not overwrite it).
-
-    The source file is closed before it is copied.
 
     \sa setFileName()
 */
@@ -867,11 +863,9 @@ QFile::copy(const QString &newName)
 /*!
     \overload
 
-    Copies the file \a fileName to \a newName. Returns \c true if successful;
+    Copies the file named \a fileName to \a newName.
-    otherwise returns \c false.
 
-    If a file with the name \a newName already exists, copy() returns \c false
+    \include qfile-copy.qdocinc
-    (i.e., QFile will not overwrite it).
 
     \sa rename()
 */