Improve the blob view experience

* Fix opening the blob view for the same file from a different commit.

* Set %(file) rather than %(file_old) in the blame view to allow the
  blob view to open properly.

* Allow faster access to the blob view when using `tig <file>`.

NEWS.adoc

@@ -15,6 +15,7 @@ Improvements:
  - Add new "prefetch" reference type for refs created by `git maintenance`
    (hidden in default config). (#1318)
  - Show the selected commit in the blame view title window.
+ - Improve the blob view experience.
 
 Bug fixes:
 

src/blame.c

@@ -482,13 +482,11 @@ blame_select(struct view *view, struct line *line)
 		string_format(view->ref, "%s changed %s", commit->id, commit->filename);
 	}
 
-	if (strcmp(commit->filename, view->env->file))
-		string_format(view->env->file_old, "%s", commit->filename);
-	else
-		view->env->file_old[0] = '\0';
+	string_ncopy(view->env->file, commit->filename, strlen(commit->filename));
 
 	view->env->lineno = view->pos.lineno + 1;
 	string_ncopy(view->env->text, text, strlen(text));
+	view->env->blob[0] = 0;
 }
 
 static struct view_ops blame_ops = {

src/blob.c

@@ -31,9 +31,19 @@ open_blob_view(struct view *prev, enum open_flags flags)
 {
 	struct view *view = &blob_view;
 	bool in_blob_view = prev == view;
-	bool has_blob_selection = view->env->blob[0] || view->env->file[0];
 
-	if (!in_blob_view && (view->lines || has_blob_selection)) {
+	if (!view->env->file[0] && opt_file_args && !opt_file_args[1]) {
+		const char *ls_tree_argv[] = {
+			"git", "ls-tree", "-d", "-z",  view->env->commit, opt_file_args[0], NULL
+		};
+		char buf[SIZEOF_STR] = "";
+
+		/* Check that opt_file_args[0] is not a directory */
+		if (!io_run_buf(ls_tree_argv, buf, sizeof(buf), NULL, false))
+			string_concat_path(view->env->file, repo.prefix, opt_file_args[0]);
+	}
+
+	if (!in_blob_view && (view->lines || view->env->blob[0] || view->env->file[0])) {
 		if (view->env->goto_lineno > 0)
 			flags |= OPEN_RELOAD;
 		open_view(prev, view, flags);

src/grep.c

@@ -86,6 +86,7 @@ grep_select(struct view *view, struct line *line)
 	string_ncopy(view->ref, grep->file, strlen(grep->file));
 	view->env->lineno = grep->lineno + 1;
 	string_ncopy(view->env->text, text, strlen(text));
+	view->env->blob[0] = 0;
 }
 
 static const char *grep_args[] = {

src/log.c

@@ -37,6 +37,7 @@ log_copy_rev(struct view *view, struct line *line)
 	size_t offset = get_graph_indent(text);
 
 	string_copy_rev_from_commit_line(view->ref, text + offset);
+	view->env->blob[0] = 0;
 }
 
 static void

src/main.c

@@ -634,6 +634,7 @@ main_select(struct view *view, struct line *line)
 			view->env->tag[0] = view->env->remote[0] = view->env->branch[0] = view->env->refname[0] = 0;
 	}
 	string_copy_rev(view->env->commit, commit->id);
+	view->env->blob[0] = 0;
 }
 
 static struct view_ops main_ops = {

src/refs.c

@@ -241,6 +241,7 @@ refs_select(struct view *view, struct line *line)
 	string_copy_rev(view->env->head, reference->ref->id);
 	string_ncopy(view->env->ref, reference->ref->name, strlen(reference->ref->name));
 	ref_update_env(view->env, reference->ref, false);
+	view->env->blob[0] = 0;
 }
 
 static struct view_ops refs_ops = {

src/stash.c

@@ -62,6 +62,7 @@ stash_select(struct view *view, struct line *line)
 	string_ncopy(view->env->stash, state->reflog[line->lineno - 1] + STRING_SIZE("refs/"),
 		     strlen(state->reflog[line->lineno - 1]) - STRING_SIZE("refs/"));
 	string_copy(view->ref, view->env->stash);
+	view->env->blob[0] = 0;
 }
 
 static enum request

src/status.c

@@ -856,8 +856,10 @@ status_select(struct view *view, struct line *line)
 
 	string_format(view->ref, text, key, file);
 	status_stage_info(view->env->status, line->type, status);
-	if (status)
+	if (status) {
 		string_copy(view->env->file, status->new.name);
+		view->env->blob[0] = 0;
+	}
 }
 
 static struct view_ops status_ops = {