Subject: Re: [PATCH/WIP v3 03/31] am: implement skeletal builtin am

From: Junio C Hamano <[email-masked]>
Date: Thu, 18 Jun 2015 13:26:08 -0700

Paul Tan <[email-masked]> writes:

> For the purpose of rewriting git-am.sh into a C builtin, implement a
> skeletal builtin/am.c that redirects to $GIT_EXEC_PATH/git-am if the
> environment variable _GIT_USE_BUILTIN_AM is not defined. Since in the
> Makefile git-am.sh takes precedence over builtin/am.c,
> $GIT_EXEC_PATH/git-am will contain the shell script git-am.sh, and thus
> this allows us to fall back on the functional git-am.sh when running the
> test suite for tests that depend on a working git-am implementation.
>
> Since git-am.sh cannot handle any environment modifications by
> setup_git_directory(), "am" has to be declared as NO_SETUP in git.c. On
> the other hand, to re-implement git-am.sh in builtin/am.c, we do need to
> run all the git dir and work tree setup logic that git.c does for us. As
> such, we work around this temporarily by copying the logic in git.c's
> run_builtin(), which amounts to:
>
> 	prefix = setup_git_directory();
> 	trace_repo_setup(prefix);
> 	setup_work_tree();
>
> This redirection should be removed when all the features of git-am.sh
> have been re-implemented in builtin/am.c.
>
> Helped-by: Junio C Hamano <[email-masked]>
> Signed-off-by: Paul Tan <[email-masked]>
> ---
>
> Notes:
>     v3
>     
>     * Style fixes
>     
>     * git-am.sh cannot handle the chdir() and GIT_DIR envionment variable
>       that setup_git_directory() sets, so we work around it by copying the
>       logic of git.c's run_builtin(), and running it only when we are using
>       the builtin am.
>
>  Makefile     |  1 +
>  builtin.h    |  1 +
>  builtin/am.c | 28 ++++++++++++++++++++++++++++
>  git.c        |  1 +
>  4 files changed, 31 insertions(+)
>  create mode 100644 builtin/am.c
>
> diff --git a/Makefile b/Makefile
> index 93e4fa2..ff9bdc0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -811,6 +811,7 @@ LIB_OBJS += xdiff-interface.o
>  LIB_OBJS += zlib.o
>  
>  BUILTIN_OBJS += builtin/add.o
> +BUILTIN_OBJS += builtin/am.o
>  BUILTIN_OBJS += builtin/annotate.o
>  BUILTIN_OBJS += builtin/apply.o
>  BUILTIN_OBJS += builtin/archive.o
> diff --git a/builtin.h b/builtin.h
> index ea3c834..f30cf00 100644
> --- a/builtin.h
> +++ b/builtin.h
> @@ -30,6 +30,7 @@ extern int textconv_object(const char *path, unsigned mode, const unsigned char
>  extern int is_builtin(const char *s);
>  
>  extern int cmd_add(int argc, const char **argv, const char *prefix);
> +extern int cmd_am(int argc, const char **argv, const char *prefix);
>  extern int cmd_annotate(int argc, const char **argv, const char *prefix);
>  extern int cmd_apply(int argc, const char **argv, const char *prefix);
>  extern int cmd_archive(int argc, const char **argv, const char *prefix);
> diff --git a/builtin/am.c b/builtin/am.c
> new file mode 100644
> index 0000000..dbc8836
> --- /dev/null
> +++ b/builtin/am.c
> @@ -0,0 +1,28 @@
> +/*
> + * Builtin "git am"
> + *
> + * Based on git-am.sh by Junio C Hamano.
> + */
> +#include "cache.h"
> +#include "builtin.h"
> +#include "exec_cmd.h"
> +
> +int cmd_am(int argc, const char **argv, const char *prefix)
> +{
> +	/*
> +	 * FIXME: Once all the features of git-am.sh have been re-implemented
> +	 * in builtin/am.c, this preamble can be removed.
> +	 */

It's not broken, so "FIXME" is not quite appropriate (and that is
why I sent you "NEEDSWORK").  Also mention that the entry in the
commands[] array needs "RUN_SETUP | NEED_WORK_TREE" added, I think.

> +	if (!getenv("_GIT_USE_BUILTIN_AM")) {
> +		const char *path = mkpath("%s/git-am", git_exec_path());
> +
> +		if (sane_execvp(path, (char **)argv) < 0)
> +			die_errno("could not exec %s", path);
> +	} else {
> +		prefix = setup_git_directory();
> +		trace_repo_setup(prefix);
> +		setup_work_tree();
> +	}
> +
> +	return 0;
> +}
> diff --git a/git.c b/git.c
> index e7a7713..a671535 100644
> --- a/git.c
> +++ b/git.c
> @@ -370,6 +370,7 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
>  
>  static struct cmd_struct commands[] = {
>  	{ "add", cmd_add, RUN_SETUP | NEED_WORK_TREE },
> +	{ "am", cmd_am, NO_SETUP },

NO_SETUP is for things like init and clone that start without a
repository and then work in the one that they create.  I think
imitating "archive" or "diff" is more appropriate.

>  	{ "annotate", cmd_annotate, RUN_SETUP },
>  	{ "apply", cmd_apply, RUN_SETUP_GENTLY },
>  	{ "archive", cmd_archive },