Fix --signTemplate double-escaping every batch after the first on Linux/macOS - #1018

--signTemplate corrupts its own command on Linux/macOS for every file after the first.

EscapeForBash(signArguments) is called inside the batching loop, so each iteration escapes an already-escaped string:

do {
    ...
    } else {
        filesToSignStr = QuoteFileArgsBash(filesToSign);
        signArguments = EscapeForBash(signArguments);   // <-- re-escapes each batch
    }

Batch 1 is correct; batch 2 has been escaped twice, batch 3 three times.

Why this isn't an edge case

A {{file}} template pins parallelism to 1, so every file is its own batch. Any template containing \, $, `, " or ' — which is most real signing commands, since credentials and URLs get quoted — fails on the second file onwards.

A {{file...}} template hits the same thing once the file count exceeds --signParallel (default 10).

Reproduction

Two files, parallelism: 1, template cp {{file}} "/tmp/out_$V.bin", driven through CodeSign.Sign on Ubuntu:

Sign() THREW: UserInfoException: Signing command failed.
Output was:
cp: cannot create regular file '"/tmp/vrepro-912b4c40/out_\$V.bin"': No such file or directory

The destination has picked up literal " and \$. The first file had already been copied correctly.

The fix

Escape once, before the loop. The filesToSignStr branch collapses to a ternary since only the quoting differs per platform now.

Tests

Three regression tests added to CodeSignTests, covering the {{file}} multi-batch path, the {{file...}} path with more files than --signParallel, and an end-to-end copy to a quoted destination across two batches.

All three fail on develop and pass with the fix:

Full Velopack.Packaging.Tests run: 86 total, 61 passed, 24 skipped, 1 failed — ResourceEditTests.CommitResourcesInCorrectOrder, which fails identically on an unmodified checkout of develop and is unrelated to this change.

Also corrected one log message: the {{file...}} branch announced itself as "a single file signing template".

_{Found while checking whether Velopack could sign Windows packages from Linux — it can, and does, which is how the multi-batch path got exercised. Disclosure: the signing tool I was driving it with is my own, but nothing here references or depends on it.}