ui-snapshot: add dwimmery

When downloading a snapshot, the snapshot name will often contain the repo
name combined with a tag. This patch tries to exploit this so that the
correct revision is downloaded even if no specific revision is specified.

PS: this only occurs if neither 'h' nor 'id' is specified in the query-
string.

PPS: this also fixes a bug which occurs when trying to download a filename
with an unsupported suffix: it used to try to print an error message to
the user but failed since it didn't prepare the output properly.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

3 files changed, 83 insertions, 15 deletions

diff --git a/cmd.c b/cmd.c
index a989220..5b3c14c 100644
--- a/cmd.c
+++ b/cmd.c
@@ -106,7 +106,7 @@ static void snapshot_fn(struct cgit_context *ctx)
 {
         cgit_print_snapshot(ctx->qry.head, ctx->qry.sha1,
                             cgit_repobasename(ctx->repo->url), ctx->qry.path,
-                            ctx->repo->snapshots);
+                            ctx->repo->snapshots, ctx->qry.nohead);
 }
 
 static void summary_fn(struct cgit_context *ctx)
diff --git a/ui-snapshot.c b/ui-snapshot.c
index 7a597ff..9c4d086 100644
--- a/ui-snapshot.c
+++ b/ui-snapshot.c
@@ -64,6 +64,22 @@ const struct cgit_snapshot_format cgit_snapshot_formats[] = {
         {}
 };
 
+static const struct cgit_snapshot_format *get_format(const char *filename)
+{
+        const struct cgit_snapshot_format *fmt;
+        int fl, sl;
+
+        fl = strlen(filename);
+        for(fmt = cgit_snapshot_formats; fmt->suffix; fmt++) {
+                sl = strlen(fmt->suffix);
+                if (sl >= fl)
+                        continue;
+                if (!strcmp(fmt->suffix, filename + fl - sl))
+                        return fmt;
+        }
+        return NULL;
+}
+
 static int make_snapshot(const struct cgit_snapshot_format *format,
                          const char *hex, const char *prefix,
                          const char *filename)
@@ -98,23 +114,75 @@ static int make_snapshot(const struct cgit_snapshot_format *format,
         return 0;
 }
 
+char *dwim_filename = NULL;
+const char *dwim_refname = NULL;
+
+static int ref_cb(const char *refname, const unsigned char *sha1, int flags,
+                  void *cb_data)
+{
+        const char *r = refname;
+        while (r && *r) {
+                fprintf(stderr, "  cmp %s with %s:", dwim_filename, r);
+                if (!strcmp(dwim_filename, r)) {
+                        fprintf(stderr, "MATCH!\n");
+                        dwim_refname = refname;
+                        return 1;
+                }
+                fprintf(stderr, "no match\n");
+                if (isdigit(*r))
+                        break;
+                r++;
+        }
+        return 0;
+}
+
+/* Try to guess the requested revision by combining repo name and tag name
+ * and comparing this to the requested snapshot name. E.g. the requested
+ * snapshot is "cgit-0.7.2.tar.gz" while repo name is "cgit" and tag name
+ * is "v0.7.2". First, the reponame is stripped off, leaving "-0.7.2.tar.gz".
+ * Next, any '-' and '_' characters are stripped, leaving "0.7.2.tar.gz".
+ * Finally, the requested format suffix is removed and we end up with "0.7.2".
+ * Then we test each tag against this dwimmed filename, and for each tag
+ * we even try to remove any leading characters which are non-digits. I.e.
+ * we first compare with "v0.7.2", then with "0.7.2" and we've got a match.
+ */
+static const char *get_ref_from_filename(const char *url, const char *filename,
+                                         const struct cgit_snapshot_format *fmt)
+{
+        const char *reponame = cgit_repobasename(url);
+        fprintf(stderr, "reponame=%s, filename=%s\n", reponame, filename);
+        if (prefixcmp(filename, reponame))
+                return NULL;
+        filename += strlen(reponame);
+        while (filename && (*filename == '-' || *filename == '_'))
+                filename++;
+        dwim_filename = xstrdup(filename);
+        dwim_filename[strlen(filename) - strlen(fmt->suffix)] = '\0';
+        for_each_tag_ref(ref_cb, NULL);
+        return dwim_refname;
+}
+
 void cgit_print_snapshot(const char *head, const char *hex, const char *prefix,
-                         const char *filename, int snapshots)
+                         const char *filename, int snapshots, int dwim)
 {
         const struct cgit_snapshot_format* f;
-        int sl, fnl;
 
-        fnl = strlen(filename);
-        if (!hex)
-                hex = head;
-        for (f = cgit_snapshot_formats; f->suffix; f++) {
-                if (!(snapshots & f->bit))
-                        continue;
-                sl = strlen(f->suffix);
-                if(fnl < sl || strcmp(&filename[fnl-sl], f->suffix))
-                        continue;
-                make_snapshot(f, hex, prefix, filename);
+        f = get_format(filename);
+        if (!f) {
+                ctx.page.mimetype = "text/html";
+                cgit_print_http_headers(&ctx);
+                cgit_print_docstart(&ctx);
+                cgit_print_pageheader(&ctx);
+                cgit_print_error(fmt("Unsupported snapshot format: %s", filename));
+                cgit_print_docend();
                 return;
         }
-        cgit_print_error(fmt("Unsupported snapshot format: %s", filename));
+
+        if (!hex && dwim)
+                hex = get_ref_from_filename(ctx.repo->url, filename, f);
+
+        if (!hex)
+                hex = head;
+
+        make_snapshot(f, hex, prefix, filename);
 }
diff --git a/ui-snapshot.h b/ui-snapshot.h
index 6e03761..3540303 100644
--- a/ui-snapshot.h
+++ b/ui-snapshot.h
@@ -3,6 +3,6 @@
 
 extern void cgit_print_snapshot(const char *head, const char *hex,
                                 const char *prefix, const char *filename,
-                                int snapshot);
+                                int snapshot, int dwim);
 
 #endif /* UI_SNAPSHOT_H */