Add version as new column in the list command table output

Add a new column in the list command output table that logs the version of the image name of the extension.
'version' of the image should be the part of the image name string that includes the version and the boot counters
at the end of the filename but excludes the .raw type suffix. This commit modifies the table outputted by the list
command to have the version from the absolute filename displayed alongside the shortened image name.

src/sysext/sysext.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <ctype.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <linux/loop.h>
@@ -2208,6 +2209,64 @@ static int vl_method_refresh(sd_varlink *link, sd_json_variant *parameters, sd_v
         return sd_varlink_reply(link, NULL);
 }
 
+static int parse_version(const char *filename, char **ret) {
+        const char *start, *last_dot_after_underscore;
+        char *version = NULL;
+
+        assert(filename);
+        assert(ret);
+
+        /* Find the last occurrences of '_'. This will mark the start of the extension version. */
+        start = strrchr(filename, '_');
+        if (!start) {
+                /* If no underscore found, assign "none" and return success.
+                * This is for cases where there are no versions in the filename like 'image.raw'. */
+                version = strdup("none");
+                if (!version)
+                        return -ENOMEM;
+                *ret = version;
+                return 0;
+        }
+        start ++;
+
+        last_dot_after_underscore = strrchr(start, '.');
+        if (!last_dot_after_underscore || (*(last_dot_after_underscore + 1) == '\0')) {
+                /* If no dot found or if dot is the last character, treat everything
+                / after '_' as the version */
+                version = strdup(start);
+                if (!version)
+                        return -ENOMEM;
+                *ret = version;
+                return 0;
+        }
+
+        if (last_dot_after_underscore[1] && isdigit(last_dot_after_underscore[1])) {
+                /* If the last dot is followed by a digit, the version is everything after the underscore
+                * This is for cases where the extension name is like so: image_0.1 */
+                version = strdup(start);
+                if (!version)
+                        return -ENOMEM;
+                *ret = version;
+        } else if (last_dot_after_underscore[1] && isalpha(last_dot_after_underscore[1])) {
+                /* If the last dot is followed by a letter, the version is between the first '_' and the last dot
+                * This is for cases where the extension name is like so: image_0.1.raw (version is 0.1)
+                * or image_1.raw (version is 1) */
+                size_t length = last_dot_after_underscore - start;
+                version = strndup(start, length);
+                if (!version)
+                        return -ENOMEM;
+                *ret = version;
+        } else {
+                /* In all other cases assign "n/a" to version */
+                version = strdup("n/a");
+                if (!version)
+                        return -ENOMEM;
+                *ret = version;
+        }
+
+        return 0;
+}
+
 static int verb_list(int argc, char **argv, void *userdata) {
         _cleanup_hashmap_free_ Hashmap *images = NULL;
         _cleanup_(table_unrefp) Table *t = NULL;
@@ -2227,14 +2286,27 @@ static int verb_list(int argc, char **argv, void *userdata) {
                 return 0;
         }
 
-        t = table_new("name", "type", "path", "time");
+        t = table_new("name", "version", "type", "path", "time");
         if (!t)
                 return log_oom();
 
         HASHMAP_FOREACH(img, images) {
+                _cleanup_free_ char *image_name = NULL, *version = NULL;
+
+                /* Get the absolute file name with version info for logging. */
+                r = path_extract_filename(img->path, &image_name);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to extract filename from '%s': %m", img->path);
+
+                /* Using the above, extract just the version part from the image name */
+                r = parse_version(image_name, &version);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to get version for the extension '%s': %m", image_name);
+
                 r = table_add_many(
                                 t,
                                 TABLE_STRING, img->name,
+                                TABLE_STRING, version,
                                 TABLE_STRING, image_type_to_string(img->type),
                                 TABLE_PATH, img->path,
                                 TABLE_TIMESTAMP, img->mtime != 0 ? img->mtime : img->crtime);