register_tempfile(): new function to handle an existing temporary file

Allow an existing file to be registered with the tempfile-handling
infrastructure; in particular, arrange for it to be deleted on program
exit. This can be used if the temporary file has to be created in a
more complicated way than just open(). For example:

* If the file itself needs to be created via the lockfile API
* If it is not a regular file (e.g., a socket)
Signed-off-by: NMichael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

tempfile.c

@@ -137,6 +137,14 @@ int create_tempfile(struct tempfile *tempfile, const char *path)
 	return tempfile->fd;
 }
 
+void register_tempfile(struct tempfile *tempfile, const char *path)
+{
+	prepare_tempfile_object(tempfile);
+	strbuf_add_absolute_path(&tempfile->filename, path);
+	tempfile->owner = getpid();
+	tempfile->active = 1;
+}
+
 int mks_tempfile_sm(struct tempfile *tempfile,
 		    const char *template, int suffixlen, int mode)
 {

tempfile.h

@@ -92,6 +92,14 @@ struct tempfile {
  */
 extern int create_tempfile(struct tempfile *tempfile, const char *path);
 
+/*
+ * Register an existing file as a tempfile, meaning that it will be
+ * deleted when the program exits. The tempfile is considered closed,
+ * but it can be worked with like any other closed tempfile (for
+ * example, it can be opened using reopen_tempfile()).
+ */
+extern void register_tempfile(struct tempfile *tempfile, const char *path);
+
 
 /*
  * mks_tempfile functions