Re: [PATCH 2/4] sequencer: add "make_patch" function to save a patch

> This function generates an informational patch file.
>
> The "make_patch" and the "get_commit" functions are copied from the
> GSoC sequencer project:
>
> git://repo.or.cz/git/sbeyer.git
>
> (commit e7b8dab0c2a73ade92017a52bb1405ea1534ef20)
>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Mentored-by: Daniel Barkalow <barkalow@iabervon.org>
> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
> ---
>  builtin-sequencer--helper.c |   75
> ++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 74
> insertions(+), 1 deletions(-)
>
> diff --git a/builtin-sequencer--helper.c b/builtin-sequencer--helper.c
> index 721c0d8..8d32480 100644
> --- a/builtin-sequencer--helper.c
> +++ b/builtin-sequencer--helper.c
> @@ -1,15 +1,83 @@
>  #include "builtin.h"
>  #include "cache.h"
>  #include "parse-options.h"
> +#include "run-command.h"
> +
> +#define SEQ_DIR "rebase-merge"
> +
> +#define PATCH_FILE	git_path(SEQ_DIR "/patch")
>
>  static const char * const git_sequencer_helper_usage[] = {
>  	"git sequencer--helper --make-patch <commit>",
>  	NULL
>  };
>
> +/* Generate purely informational patch file */
> +static void make_patch(struct commit *commit)
> +{
> +	struct commit_list *parents = commit->parents;
> +	const char **args;
> +	struct child_process chld;
> +	int fd = open(PATCH_FILE, O_WRONLY | O_CREAT, 0666);
> +	if (fd < 0)
> +		return;
> +
> +	memset(&chld, 0, sizeof(chld));
> +	if (!parents) {
> +		write(fd, "Root commit\n", 12);
> +		close(fd);
> +		return;
> +	} else if (!parents->next) {
> +		args = xcalloc(5, sizeof(char *));
> +		args[0] = "diff-tree";
> +		args[1] = "-p";
> +		args[2] = xstrdup(sha1_to_hex(parents->item->object.sha1));
> +		args[3] = xstrdup(sha1_to_hex(((struct object *)commit)->sha1));
> +	} else {
> +		int i = 0;
> +		int count = 1;
> +
> +		for (; parents; parents = parents->next)
> +			++count;
> +		args = xcalloc(count + 3, sizeof(char *));
> +		args[i++] = "diff";
> +		args[i++] = "--cc";
> +		args[i++] = xstrdup(sha1_to_hex(commit->object.sha1));
> +
> +		for (parents = commit->parents; parents;
> +		     parents = parents->next)
> +			args[i++] = xstrdup(sha1_to_hex(
> +					    parents->item->object.sha1));
> +	}
> +
> +	chld.argv = args;
> +	chld.git_cmd = 1;
> +	chld.out = fd;
> +
> +	/* Run, ignore errors. */
> +	if (start_command(&chld))
> +		return;
> +	finish_command(&chld);
> +
> +	/* TODO: free dup'ed SHAs in argument list */
> +}
> +
> +/* Return a commit object of "arg" */
> +static struct commit *get_commit(const char *arg)
> +{
> +	unsigned char sha1[20];
> +
> +	if (get_sha1(arg, sha1)) {
> +		error("Could not find '%s'", arg);
> +		return NULL;
> +	}
> +	return lookup_commit_reference(sha1);
> +}
> +
>  int cmd_sequencer__helper(int argc, const char **argv, const char
> *prefix) {
>  	char *commit = NULL;
> +	struct commit *c;
>  	struct option options[] = {
>  		OPT_STRING(0, "make-patch", &commit, "commit",
>  			   "create a patch from commit"),
> @@ -22,6 +90,11 @@ int cmd_sequencer__helper(int argc, const char **argv,
> const char *prefix) if (!commit)
>  		usage_with_options(git_sequencer_helper_usage, options);
>
> -	/* Nothing to do yet */
> +	c = get_commit(commit);
> +	if (!c)
> +		return 1;
> +
> +	make_patch(c);
> +
>  	return 0;
>  }