text: use mkstemp(3) for temporary file creation in atomic saves

Instead of simply appending a tilde to the original file name, we now
create an unique temporary file based on the pattern `.filename.vis.XXXXXX`.

In case the file does not yet exist, we use 0666 & ~umask as permission,
(this should match the previous `open(2)` based behavior).

1 files changed, 4 insertions, 3 deletions

diff --git a/text.h b/text.h
index 06b7843..2fa6aea 100644
--- a/text.h
+++ b/text.h
@@ -280,9 +280,10 @@ enum TextSaveMethod {
 	/**
 	 * Save file atomically using `rename(2)`.
 	 *
-	 * Creates a new file named `filename~` and tries to restore all important
-	 * meta data. After which it is atomically moved to its final
-	 * (possibly already existing) destination using `rename(2)`.
+	 * Creates a temporary file, restores all important meta data,
+	 * before moving it atomically to its final (possibly already
+	 * existing) destination using `rename(2)`. For new files,
+	 * permissions are set to `0666 & ~umask`.
 	 *
 	 * @rst
 	 * .. warning:: This approach does not work if: