@@ -361,6 +361,58 @@ static int index_to_zip(const char *git_dir)
 	return run_command(&cp);
 }
 
+#ifndef WIN32
+#include <sys/statvfs.h>
+#endif
+
+static int get_disk_info(struct strbuf *out)
+{
+#ifdef WIN32
+	struct strbuf buf = STRBUF_INIT;
+	char volume_name[MAX_PATH], fs_name[MAX_PATH];
+	DWORD serial_number, component_length, flags;
+	ULARGE_INTEGER avail2caller, total, avail;
+
+	strbuf_realpath(&buf, ".", 1);
+	if (!GetDiskFreeSpaceExA(buf.buf, &avail2caller, &total, &avail)) {
+		error(_("could not determine free disk size for '%s'"),
+		      buf.buf);
+		strbuf_release(&buf);
+		return -1;
+	}
+
+	strbuf_setlen(&buf, offset_1st_component(buf.buf));
+	if (!GetVolumeInformationA(buf.buf, volume_name, sizeof(volume_name),
+				   &serial_number, &component_length, &flags,
+				   fs_name, sizeof(fs_name))) {
+		error(_("could not get info for '%s'"), buf.buf);
+		strbuf_release(&buf);
+		return -1;
+	}
+	strbuf_addf(out, "Available space on '%s': ", buf.buf);
+	strbuf_humanise_bytes(out, avail2caller.QuadPart);
+	strbuf_addch(out, '\n');
+	strbuf_release(&buf);
+#else
+	struct strbuf buf = STRBUF_INIT;
+	struct statvfs stat;
+
+	strbuf_realpath(&buf, ".", 1);
+	if (statvfs(buf.buf, &stat) < 0) {
+		error_errno(_("could not determine free disk size for '%s'"),
+			    buf.buf);
+		strbuf_release(&buf);
+		return -1;
+	}
+
+	strbuf_addf(out, "Available space on '%s': ", buf.buf);
+	strbuf_humanise_bytes(out, st_mult(stat.f_bsize, stat.f_bavail));
+	strbuf_addf(out, " (mount flags 0x%lx)\n", stat.f_flag);
+	strbuf_release(&buf);
+#endif
+	return 0;
+}
+
 /* printf-style interface, expects `<key>=<value>` argument */
 static int set_config(const char *fmt, ...)
 {

@@ -637,6 +689,7 @@ static int cmd_diagnose(int argc, const char **argv)
 	get_version_info(&buf, 1);
 
 	strbuf_addf(&buf, "Enlistment root: %s\n", the_repository->worktree);
+	get_disk_info(&buf);
 	fwrite(buf.buf, buf.len, 1, stdout);
 
 	if ((res = stage(tmp_dir.buf, &buf, "diagnostics.log")))