[PATCH 14/14] clone: give advice on how to resume a failed clone

[Jeff King <peff@peff.net>]

When clone fails, we usually delete the partial directory.
However, if cloning was fetching a bundle, that is resumable
and we should consider those results precious.

This patch detects when a partial bundle is present,
preserves the directory, and gives the user some advice
about how to resume.

Signed-off-by: Jeff King <peff@peff.net>
---
We could make "git clone ..." automatically resume, but I'm a little
nervous about that. I wrote a patch that did so, and it did work, but
there are a lot of little hiccups as we violate the assumption that the
directory didn't already exist (e.g., it writes multiple fetch refspec
lines to the config).

But more importantly, I really worry about destroying the safety valve
of not overwriting an existing directory. Yes, we can check to see that
it is a git directory and that it has a partially-downloaded bundle
file. But that could also describe an existing git repo with unstaged
changes. And you sure don't want to "checkout -f" over them.

So I'd rather at least start with giving the user some advice and
having them explicitly say "yeah, I do want to resume this".

 builtin/clone.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index efe8b6c..c242e20 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -392,6 +392,36 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
 	return ret;
 }
 
+static int git_dir_is_resumable(const char *dir)
+{
+	const char *objects = mkpath("%s/objects", dir);
+	DIR *dh = opendir(objects);
+	struct dirent *de;
+
+	if (!dh)
+		return 0;
+
+	while ((de = readdir(dh))) {
+		if (!prefixcmp(de->d_name, "tmp_bundle_")) {
+			closedir(dh);
+			return 1;
+		}
+	}
+
+	closedir(dh);
+	return 0;
+}
+
+static void give_resume_advice(void)
+{
+	advise("Cloning failed, but partial results were saved.");
+	advise("You can resume the fetch with:");
+	advise("  git fetch");
+	if (!option_bare)
+		advise("  git checkout %s",
+		       option_branch ? option_branch : "master");
+}
+
 static const char *junk_work_tree;
 static const char *junk_git_dir;
 static pid_t junk_pid;
@@ -402,6 +432,10 @@ static void remove_junk(void)
 	if (getpid() != junk_pid)
 		return;
 	if (junk_git_dir) {
+		if (git_dir_is_resumable(junk_git_dir)) {
+			give_resume_advice();
+			return;
+		}
 		strbuf_addstr(&sb, junk_git_dir);
 		remove_dir_recursively(&sb, 0);
 		strbuf_reset(&sb);
-- 
1.7.7.2.7.g9f96f