fix(signatures): match the guard against on-disk text, newline and all

The guard compared the buffer block, with trailing blank lines trimmed,
against knownSignatures() values returned verbatim by text(), which carry
the trailing newline every editor writes. The two never compared equal, so
a signature read back from disk was always treated as unknown: switching
appended a second signature instead of replacing, and None removed nothing.

Normalise each known entry the same way the block scan does, once in
replace(), rather than per comparison.

Part of item 152.

1 files changed, 24 insertions, 1 deletions

diff --git a/src/signatures.cpp b/src/signatures.cpp
index eb43048..ef631d6 100644
--- a/src/signatures.cpp
+++ b/src/signatures.cpp
@@ -69,6 +69,20 @@ bool isQuoted(const QString &line)
     return line.startsWith(QLatin1Char('>'));
 }
 
+/// \p text with trailing blank lines removed, the same normalisation the block
+/// scan below applies. text() returns file content verbatim, so a signature
+/// file ends with the newline every editor writes; without this the match
+/// compares a block with no trailing newline against a known entry that has
+/// one, and the guard silently fails, appending a second signature instead of
+/// replacing the first.
+QString stripTrailingBlankLines(const QString &text)
+{
+    QStringList lines = text.split(QLatin1Char('\n'));
+    while (!lines.isEmpty() && lines.last().trimmed().isEmpty())
+        lines.removeLast();
+    return lines.join(QLatin1Char('\n'));
+}
+
 /// The index of the first line of the quote, or -1 when the buffer has none.
 ///
 /// The attribution line ("On Mon, someone wrote:") is deliberately NOT
@@ -164,9 +178,18 @@ QStringList withoutSignature(const QStringList &lines, int delimiter)
 QString replace(const QString &buffer, const QString &signature,
                 const QStringList &known, Position position)
 {
+    // Normalise known to the same footing the block scan uses, once here rather
+    // than per comparison. knownSignatures() passes text() verbatim, trailing
+    // newline and all, and the match must be newline-insensitive or the guard
+    // treats every on-disk signature as unknown.
+    QStringList normalized;
+    normalized.reserve(known.size());
+    for (const QString &entry : known)
+        normalized.append(stripTrailingBlankLines(entry));
+
     QStringList lines = buffer.split(QLatin1Char('\n'));
 
-    const int existing = existingSignature(lines, known);
+    const int existing = existingSignature(lines, normalized);
     if (existing >= 0)
         lines = withoutSignature(lines, existing);