Fix `exiv2`: verbose extract stdout mutli-file (#2068)

When using `exiv2 --verbose --extract` with stdout and multiple files, the output is concatenated together.

exiv2.md

@@ -660,7 +660,7 @@ Extract target(s) for the [extract](#ex_extract) action. Possible targets are:
 | C                | Extract ICC profile, to a file called *\<file\>.icc* (see [ICC PROFILES](#icc_profiles)) |
 | X                | Extract metadata to an XMP sidecar file, \<file\>.xmp. Other targets cannot be used with this, as only XMP data is written. Extracted XMP tags include those converted from Exif and IPTC |
 | XX               | Extract "raw" metadata to a sidecar file, \<file\>.exv. The remaining targets determine which metadata to include, possible are Exif and IPTC (XMP is always included) |
-| -                | Output to stdout (see [--insert tgt2](#insert_tgt2) for an example of this feature). This argument ignores [--verbose](#verbose) |
+| -                | Output to stdout (see example in [--insert tgt2](#insert_tgt2)). This ignores [--verbose](#verbose) and only allows extracting from 1 file |
 
 To extract to a location other than the current directory, use [--location dir](#location_dir). 
 

src/exiv2.cpp

@@ -159,6 +159,11 @@ int main(int argc, char* const argv[])
         // Process all files
         int n = 1;
         int s = static_cast<int>(params.files_.size());
+        if (params.action_ & Action::extract && params.target_ & Params::ctStdInOut && s > 1) {
+            std::cerr << params.progname() << ": " << _("Only one file is allowed when extracting to stdout") << std::endl;
+            rc = 1;
+        }
+        else {
             int w = s > 9 ? s > 99 ? 3 : 2 : 1;
             for (auto&& file : params.files_) {
                 // If extracting to stdout then ignore verbose
@@ -175,7 +180,7 @@ int main(int argc, char* const argv[])
             taskFactory.cleanup();
             Params::cleanup();
             Exiv2::XmpParser::terminate();
-
+        }
     } catch (const std::exception& exc) {
         std::cerr << "Uncaught exception: " << exc.what() << std::endl;
         rc = 1;

tests/bugfixes/github/test_pr_2068.py

@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+
+import system_tests
+from system_tests import CaseMeta, path
+
+class TestVerboseExtractStdoutMultiFile(metaclass=CaseMeta):
+
+    filename = path("$data_path/exiv2-empty.jpg")
+    commands = ["$exiv2 --verbose --extract X- $filename $filename"]
+
+    stdout = [""""""]
+
+    stderr = ["""exiv2: Only one file is allowed when extracting to stdout
+"""]
+    retval = [1]
+