1 files changed, 21 insertions, 5 deletions

diff --git a/ui-shared.c b/ui-shared.c
index 562fa0e..b1a6c46 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -1069,18 +1069,34 @@ void cgit_print_filemode(unsigned short mode)
         html_fileperm(mode);
 }
 
+void cgit_compose_snapshot_prefix(struct strbuf *filename, const char *base,
+                                  const char *ref)
+{
+        unsigned char sha1[20];
+
+        /*
+         * Prettify snapshot names by stripping leading "v" or "V" if the tag
+         * name starts with {v,V}[0-9] and the prettify mapping is injective,
+         * i.e. each stripped tag can be inverted without ambiguities.
+         */
+        if (get_sha1(fmt("refs/tags/%s", ref), sha1) == 0 &&
+            (ref[0] == 'v' || ref[0] == 'V') && isdigit(ref[1]) &&
+            ((get_sha1(fmt("refs/tags/%s", ref + 1), sha1) == 0) +
+             (get_sha1(fmt("refs/tags/v%s", ref + 1), sha1) == 0) +
+             (get_sha1(fmt("refs/tags/V%s", ref + 1), sha1) == 0) == 1))
+                ref++;
+
+        strbuf_addf(filename, "%s-%s", base, ref);
+}
+
 void cgit_print_snapshot_links(const char *repo, const char *head,
                                const char *hex, int snapshots)
 {
         const struct cgit_snapshot_format* f;
         struct strbuf filename = STRBUF_INIT;
         size_t prefixlen;
-        unsigned char sha1[20];
 
-        if (get_sha1(fmt("refs/tags/%s", hex), sha1) == 0 &&
-            (hex[0] == 'v' || hex[0] == 'V') && isdigit(hex[1]))
-                hex++;
-        strbuf_addf(&filename, "%s-%s", cgit_repobasename(repo), hex);
+        cgit_compose_snapshot_prefix(&filename, cgit_repobasename(repo), hex);
         prefixlen = filename.len;
         for (f = cgit_snapshot_formats; f->suffix; f++) {
                 if (!(snapshots & f->bit))