[PATCH] interpret-trailers: add option for in-place editing

[PATCH] interpret-trailers: add option for in-place editing

[Tobias Klauser]

From: Tobias Klauser <tklauser@distanz.ch>

Add a command line option --in-place to support in-place editing akin to
sed -i.  This allows to write commands like the following:

  git interpret-trailers --trailer "X: Y" a.txt > b.txt && mv b.txt a.txt

in a more concise way:

  git interpret-trailers --trailer "X: Y" --in-place a.txt

Also add the corresponding documentation and tests.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
---
 Documentation/git-interpret-trailers.txt | 24 +++++++++++++++++++-
 builtin/interpret-trailers.c             | 13 +++++++----
 t/t7513-interpret-trailers.sh            | 32 ++++++++++++++++++++++++++
 trailer.c                                | 39 ++++++++++++++++++++------------
 trailer.h                                |  3 ++-
 5 files changed, 91 insertions(+), 20 deletions(-)

diff --git a/Documentation/git-interpret-trailers.txt b/Documentation/git-interpret-trailers.txt
index 0ecd497c4de7..a77b901f1d7b 100644
--- a/Documentation/git-interpret-trailers.txt
+++ b/Documentation/git-interpret-trailers.txt
@@ -8,7 +8,7 @@ git-interpret-trailers - help add structured information into commit messages
 SYNOPSIS
 --------
 [verse]
-'git interpret-trailers' [--trim-empty] [(--trailer <token>[(=|:)<value>])...] [<file>...]
+'git interpret-trailers' [--in-place] [--trim-empty] [(--trailer <token>[(=|:)<value>])...] [<file>...]
 
 DESCRIPTION
 -----------
@@ -64,6 +64,9 @@ folding rules, the encoding rules and probably many other rules.
 
 OPTIONS
 -------
+--in-place::
+	Edit the files in place.
+
 --trim-empty::
 	If the <value> part of any trailer contains only whitespace,
 	the whole trailer will be removed from the resulting message.
@@ -216,6 +219,25 @@ Signed-off-by: Alice <alice@example.com>
 Signed-off-by: Bob <bob@example.com>
 ------------
 
+* Use the '--in-place' option to edit a message file in place:
++
+------------
+$ cat msg.txt
+subject
+
+message
+
+Signed-off-by: Bob <bob@example.com>
+$ git interpret-trailers --trailer 'Acked-by: Alice <alice@example.com>' --in-place msg.txt
+$ cat msg.txt
+subject
+
+message
+
+Signed-off-by: Bob <bob@example.com>
+Acked-by: Alice <alice@example.com>
+------------
+
 * Extract the last commit as a patch, and add a 'Cc' and a
   'Reviewed-by' trailer to it:
 +
diff --git a/builtin/interpret-trailers.c b/builtin/interpret-trailers.c
index 46838d24a90a..b99ae4be8875 100644
--- a/builtin/interpret-trailers.c
+++ b/builtin/interpret-trailers.c
@@ -12,16 +12,18 @@
 #include "trailer.h"
 
 static const char * const git_interpret_trailers_usage[] = {
-	N_("git interpret-trailers [--trim-empty] [(--trailer <token>[(=|:)<value>])...] [<file>...]"),
+	N_("git interpret-trailers [--in-place] [--trim-empty] [(--trailer <token>[(=|:)<value>])...] [<file>...]"),
 	NULL
 };
 
 int cmd_interpret_trailers(int argc, const char **argv, const char *prefix)
 {
+	int in_place = 0;
 	int trim_empty = 0;
 	struct string_list trailers = STRING_LIST_INIT_DUP;
 
 	struct option options[] = {
+		OPT_BOOL(0, "in-place", &in_place, N_("edit files in place")),
 		OPT_BOOL(0, "trim-empty", &trim_empty, N_("trim empty trailers")),
 		OPT_STRING_LIST(0, "trailer", &trailers, N_("trailer"),
 				N_("trailer(s) to add")),
@@ -34,9 +36,12 @@ int cmd_interpret_trailers(int argc, const char **argv, const char *prefix)
 	if (argc) {
 		int i;
 		for (i = 0; i < argc; i++)
-			process_trailers(argv[i], trim_empty, &trailers);
-	} else
-		process_trailers(NULL, trim_empty, &trailers);
+			process_trailers(argv[i], in_place, trim_empty, &trailers);
+	} else {
+		if (in_place)
+			die(_("no input file given for in-place editing"));
+		process_trailers(NULL, in_place, trim_empty, &trailers);
+	}
 
 	string_list_clear(&trailers, 0);
 
diff --git a/t/t7513-interpret-trailers.sh b/t/t7513-interpret-trailers.sh
index 322c436a494c..1103a4838b5c 100755
--- a/t/t7513-interpret-trailers.sh
+++ b/t/t7513-interpret-trailers.sh
@@ -326,6 +326,38 @@ test_expect_success 'with complex patch, args and --trim-empty' '
 	test_cmp expected actual
 '
 
+test_expect_success 'in-place editing with basic patch' '
+	cat basic_message >message &&
+	cat basic_patch >>message &&
+	cat basic_message >expected &&
+	echo >>expected &&
+	cat basic_patch >>expected &&
+	git interpret-trailers --in-place message &&
+	test_cmp expected message
+'
+
+test_expect_success 'in-place editing with additional trailer' '
+	cat basic_message >message &&
+	cat basic_patch >>message &&
+	cat basic_message >expected &&
+	echo >>expected &&
+	cat >>expected <<-\EOF &&
+		Reviewed-by: Alice
+	EOF
+	cat basic_patch >>expected &&
+	git interpret-trailers --trailer "Reviewed-by: Alice" --in-place message &&
+	test_cmp expected message
+'
+
+test_expect_success 'in-place editing on stdin' '
+	test_must_fail git interpret-trailers --trailer "Reviewed-by: Alice" --in-place < basic_message
+'
+
+test_expect_success 'in-place editing on non-existing file' '
+	test_must_fail git interpret-trailers --trailer "Reviewed-by: Alice" --in-place nonexisting &&
+	test_path_is_missing nonexisting
+'
+
 test_expect_success 'using "where = before"' '
 	git config trailer.bug.where "before" &&
 	cat complex_message_body >expected &&
diff --git a/trailer.c b/trailer.c
index 6f3416febaba..e05fa0e9ce93 100644
--- a/trailer.c
+++ b/trailer.c
@@ -108,23 +108,23 @@ static char last_non_space_char(const char *s)
 	return '\0';
 }
 
-static void print_tok_val(const char *tok, const char *val)
+static void print_tok_val(FILE *fp, const char *tok, const char *val)
 {
 	char c = last_non_space_char(tok);
 	if (!c)
 		return;
 	if (strchr(separators, c))
-		printf("%s%s\n", tok, val);
+		fprintf(fp, "%s%s\n", tok, val);
 	else
-		printf("%s%c %s\n", tok, separators[0], val);
+		fprintf(fp, "%s%c %s\n", tok, separators[0], val);
 }
 
-static void print_all(struct trailer_item *first, int trim_empty)
+static void print_all(FILE *fp, struct trailer_item *first, int trim_empty)
 {
 	struct trailer_item *item;
 	for (item = first; item; item = item->next) {
 		if (!trim_empty || strlen(item->value) > 0)
-			print_tok_val(item->token, item->value);
+			print_tok_val(fp, item->token, item->value);
 	}
 }
 
@@ -795,14 +795,15 @@ static int has_blank_line_before(struct strbuf **lines, int start)
 	return 0;
 }
 
-static void print_lines(struct strbuf **lines, int start, int end)
+static void print_lines(FILE *fp, struct strbuf **lines, int start, int end)
 {
 	int i;
 	for (i = start; lines[i] && i < end; i++)
-		printf("%s", lines[i]->buf);
+		fprintf(fp, "%s", lines[i]->buf);
 }
 
-static int process_input_file(struct strbuf **lines,
+static int process_input_file(FILE *fp,
+			      struct strbuf **lines,
 			      struct trailer_item **in_tok_first,
 			      struct trailer_item **in_tok_last)
 {
@@ -818,10 +819,10 @@ static int process_input_file(struct strbuf **lines,
 	trailer_start = find_trailer_start(lines, trailer_end);
 
 	/* Print lines before the trailers as is */
-	print_lines(lines, 0, trailer_start);
+	print_lines(fp, lines, 0, trailer_start);
 
 	if (!has_blank_line_before(lines, trailer_start - 1))
-		printf("\n");
+		fprintf(fp, "\n");
 
 	/* Parse trailer lines */
 	for (i = trailer_start; i < trailer_end; i++) {
@@ -842,13 +843,14 @@ static void free_all(struct trailer_item **first)
 	}
 }
 
-void process_trailers(const char *file, int trim_empty, struct string_list *trailers)
+void process_trailers(const char *file, int in_place, int trim_empty, struct string_list *trailers)
 {
 	struct trailer_item *in_tok_first = NULL;
 	struct trailer_item *in_tok_last = NULL;
 	struct trailer_item *arg_tok_first;
 	struct strbuf **lines;
 	int trailer_end;
+	FILE *fp = stdout;
 
 	/* Default config must be setup first */
 	git_config(git_trailer_default_config, NULL);
@@ -856,19 +858,28 @@ void process_trailers(const char *file, int trim_empty, struct string_list *trai
 
 	lines = read_input_file(file);
 
+	if (in_place) {
+		fp = fopen(file, "w");
+		if (!fp)
+			die_errno(_("could not open file '%s' for writing"), file);
+	}
+
 	/* Print the lines before the trailers */
-	trailer_end = process_input_file(lines, &in_tok_first, &in_tok_last);
+	trailer_end = process_input_file(fp, lines, &in_tok_first, &in_tok_last);
 
 	arg_tok_first = process_command_line_args(trailers);
 
 	process_trailers_lists(&in_tok_first, &in_tok_last, &arg_tok_first);
 
-	print_all(in_tok_first, trim_empty);
+	print_all(fp, in_tok_first, trim_empty);
 
 	free_all(&in_tok_first);
 
 	/* Print the lines after the trailers as is */
-	print_lines(lines, trailer_end, INT_MAX);
+	print_lines(fp, lines, trailer_end, INT_MAX);
+
+	if (in_place)
+		fclose(fp);
 
 	strbuf_list_free(lines);
 }
diff --git a/trailer.h b/trailer.h
index 8eb25d565e28..36b40b81761f 100644
--- a/trailer.h
+++ b/trailer.h
@@ -1,6 +1,7 @@
 #ifndef TRAILER_H
 #define TRAILER_H
 
-void process_trailers(const char *file, int trim_empty, struct string_list *trailers);
+void process_trailers(const char *file, int in_place, int trim_empty,
+		      struct string_list *trailers);
 
 #endif /* TRAILER_H */
-- 
2.6.3.368.gf34be46.dirty

Re: [PATCH] interpret-trailers: add option for in-place editing

[Matthieu Moy]

Tobias Klauser <tobias.klauser@zhinst.com> writes:

> From: Tobias Klauser <tklauser@distanz.ch>
>
> Add a command line option --in-place to support in-place editing akin to
> sed -i.  This allows to write commands like the following:

Since -i is a common shortcut for --in-place (perl -i, sed -i), it
probably makes sense to have it here too. OTOH, this is meant for
scripting and perhaps it's best to force script writters to be verbose.

> Also add the corresponding documentation and tests.

This sentence does not harm, but I personnally don't think it's really
helpfull, as it's already clear by the diffstat right below, and the
patch itself.

> -static void print_tok_val(const char *tok, const char *val)
> +static void print_tok_val(FILE *fp, const char *tok, const char *val)
>  {
>  	char c = last_non_space_char(tok);
>  	if (!c)
>  		return;
>  	if (strchr(separators, c))
> -		printf("%s%s\n", tok, val);
> +		fprintf(fp, "%s%s\n", tok, val);
>  	else
> -		printf("%s%c %s\n", tok, separators[0], val);
> +		fprintf(fp, "%s%c %s\n", tok, separators[0], val);
>  }

The patch would be even easier to read if split into a preparatory
refactoring patch "turn printf into fprintf" and then the actual one.
But it's already rather clear, so you can probably leave it as-is.

> -static void print_lines(struct strbuf **lines, int start, int end)
> +static void print_lines(FILE *fp, struct strbuf **lines, int start, int end)

Here and below: it would probably be more readable with a more explicit
name for fp, like "outfile". Especially here:

> -static int process_input_file(struct strbuf **lines,
> +static int process_input_file(FILE *fp,
> +			      struct strbuf **lines,

Where it's tempting to think that a parameter given to
process_input_file is ... the input file!

Other than these minor details, the patch looks good to me. Thanks for
the patch!

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: [PATCH] interpret-trailers: add option for in-place editing

[Tobias Klauser]

Thanks for your feedback Matthieu!

On 2016-01-06 at 15:19:45 +0100, Matthieu Moy <Matthieu.Moy@grenoble-inp.fr> wrote:
> Tobias Klauser <tobias.klauser@zhinst.com> writes:
> 
> > From: Tobias Klauser <tklauser@distanz.ch>
> >
> > Add a command line option --in-place to support in-place editing akin to
> > sed -i.  This allows to write commands like the following:
> 
> Since -i is a common shortcut for --in-place (perl -i, sed -i), it
> probably makes sense to have it here too. OTOH, this is meant for
> scripting and perhaps it's best to force script writters to be verbose.

Yes, I thought this would mainly be used in scripts and thus omitted the
short option.

> > Also add the corresponding documentation and tests.
> 
> This sentence does not harm, but I personnally don't think it's really
> helpfull, as it's already clear by the diffstat right below, and the
> patch itself.

Ok, I can omit it for v2.

> > -static void print_tok_val(const char *tok, const char *val)
> > +static void print_tok_val(FILE *fp, const char *tok, const char *val)
> >  {
> >  	char c = last_non_space_char(tok);
> >  	if (!c)
> >  		return;
> >  	if (strchr(separators, c))
> > -		printf("%s%s\n", tok, val);
> > +		fprintf(fp, "%s%s\n", tok, val);
> >  	else
> > -		printf("%s%c %s\n", tok, separators[0], val);
> > +		fprintf(fp, "%s%c %s\n", tok, separators[0], val);
> >  }
> 
> The patch would be even easier to read if split into a preparatory
> refactoring patch "turn printf into fprintf" and then the actual one.
> But it's already rather clear, so you can probably leave it as-is.

Ok. I have also no problem with splitting it. I'll wait for a feedback
from Junio on what he prefers.

> > -static void print_lines(struct strbuf **lines, int start, int end)
> > +static void print_lines(FILE *fp, struct strbuf **lines, int start, int end)
> 
> Here and below: it would probably be more readable with a more explicit
> name for fp, like "outfile". Especially here:
> 
> > -static int process_input_file(struct strbuf **lines,
> > +static int process_input_file(FILE *fp,
> > +			      struct strbuf **lines,
> 
> Where it's tempting to think that a parameter given to
> process_input_file is ... the input file!

Yes, makes sense. I'll change it to a more concise and readable name
I'd also take "outfile" as you suggest, unless anyone objects.

Thanks
Tobias

Re: [PATCH] interpret-trailers: add option for in-place editing

[Eric Sunshine]

On Wed, Jan 6, 2016 at 8:34 AM, Tobias Klauser
<tobias.klauser@zhinst.com> wrote:
> Add a command line option --in-place to support in-place editing akin to
> sed -i.  This allows to write commands like the following:
>
>   git interpret-trailers --trailer "X: Y" a.txt > b.txt && mv b.txt a.txt
>
> in a more concise way:
>
>   git interpret-trailers --trailer "X: Y" --in-place a.txt
>
> Also add the corresponding documentation and tests.

In addition to Matthieu's comments...

> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
> diff --git a/trailer.c b/trailer.c
> @@ -856,19 +858,28 @@ void process_trailers(const char *file, int trim_empty, struct string_list *trai
>
>         lines = read_input_file(file);
>
> +       if (in_place) {
> +               fp = fopen(file, "w");
> +               if (!fp)
> +                       die_errno(_("could not open file '%s' for writing"), file);
> +       }

The input file should be considered precious, but this implementation
plays too loosely with it. If the user interrupts the program or a
die() somewhere within the "trailers" code aborts the program before
the output file is written, then the original file will be
irrecoverably lost. Users won't be happy about that.

Instead, this code should go through the standard dance of writing the
output to a new file (with some unique temporary name) and then, only
once the output has been successfully written in full, rename the new
file atop the old.

>         /* Print the lines before the trailers */
> -       trailer_end = process_input_file(lines, &in_tok_first, &in_tok_last);
> +       trailer_end = process_input_file(fp, lines, &in_tok_first, &in_tok_last);
>
>         arg_tok_first = process_command_line_args(trailers);
>
>         process_trailers_lists(&in_tok_first, &in_tok_last, &arg_tok_first);
>
> -       print_all(in_tok_first, trim_empty);
> +       print_all(fp, in_tok_first, trim_empty);
>
>         free_all(&in_tok_first);
>
>         /* Print the lines after the trailers as is */
> -       print_lines(lines, trailer_end, INT_MAX);
> +       print_lines(fp, lines, trailer_end, INT_MAX);
> +
> +       if (in_place)
> +               fclose(fp);
>
>         strbuf_list_free(lines);
>  }

Re: [PATCH] interpret-trailers: add option for in-place editing

[Tobias Klauser]

On 2016-01-06 at 20:02:23 +0100, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Wed, Jan 6, 2016 at 8:34 AM, Tobias Klauser
> <tobias.klauser@zhinst.com> wrote:
> > Add a command line option --in-place to support in-place editing akin to
> > sed -i.  This allows to write commands like the following:
> >
> >   git interpret-trailers --trailer "X: Y" a.txt > b.txt && mv b.txt a.txt
> >
> > in a more concise way:
> >
> >   git interpret-trailers --trailer "X: Y" --in-place a.txt
> >
> > Also add the corresponding documentation and tests.
> 
> In addition to Matthieu's comments...
> 
> > Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> > ---
> > diff --git a/trailer.c b/trailer.c
> > @@ -856,19 +858,28 @@ void process_trailers(const char *file, int trim_empty, struct string_list *trai
> >
> >         lines = read_input_file(file);
> >
> > +       if (in_place) {
> > +               fp = fopen(file, "w");
> > +               if (!fp)
> > +                       die_errno(_("could not open file '%s' for writing"), file);
> > +       }
> 
> The input file should be considered precious, but this implementation
> plays too loosely with it. If the user interrupts the program or a
> die() somewhere within the "trailers" code aborts the program before
> the output file is written, then the original file will be
> irrecoverably lost. Users won't be happy about that.

Indeed, I didn't consider this. Thanks a lot for pointing this out.

> Instead, this code should go through the standard dance of writing the
> output to a new file (with some unique temporary name) and then, only
> once the output has been successfully written in full, rename the new
> file atop the old.

Ok, will do this for v2. I guess with the help of the functions from
tempfile.h it should be fairly easy to implement...

Thanks for your review!