interpret-trailers: add option for in-place editing

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

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 40 insertions, 1 deletions

diff --git a/trailer.c b/trailer.c
index 176fac2..94b387b 100644
--- a/trailer.c
+++ b/trailer.c
@@ -2,6 +2,7 @@
 #include "string-list.h"
 #include "run-command.h"
 #include "commit.h"
+#include "tempfile.h"
 #include "trailer.h"
 /*
  * Copyright (c) 2013, 2014 Christian Couder <chriscool@tuxfamily.org>
@@ -843,7 +844,38 @@ static void free_all(struct trailer_item **first)
 	}
 }
 
-void process_trailers(const char *file, int trim_empty, struct string_list *trailers)
+static struct tempfile trailers_tempfile;
+
+static FILE *create_in_place_tempfile(const char *file)
+{
+	struct stat st;
+	struct strbuf template = STRBUF_INIT;
+	const char *tail;
+	FILE *outfile;
+
+	if (stat(file, &st))
+		die_errno(_("could not stat %s"), file);
+	if (!S_ISREG(st.st_mode))
+		die(_("file %s is not a regular file"), file);
+	if (!(st.st_mode & S_IWUSR))
+		die(_("file %s is not writable by user"), file);
+
+	/* Create temporary file in the same directory as the original */
+	tail = strrchr(file, '/');
+	if (tail != NULL)
+		strbuf_add(&template, file, tail - file + 1);
+	strbuf_addstr(&template, "git-interpret-trailers-XXXXXX");
+
+	xmks_tempfile_m(&trailers_tempfile, template.buf, st.st_mode);
+	strbuf_release(&template);
+	outfile = fdopen_tempfile(&trailers_tempfile, "w");
+	if (!outfile)
+		die_errno(_("could not open temporary file"));
+
+	return outfile;
+}
+
+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;
@@ -858,6 +890,9 @@ void process_trailers(const char *file, int trim_empty, struct string_list *trai
 
 	lines = read_input_file(file);
 
+	if (in_place)
+		outfile = create_in_place_tempfile(file);
+
 	/* Print the lines before the trailers */
 	trailer_end = process_input_file(outfile, lines, &in_tok_first, &in_tok_last);
 
@@ -872,5 +907,9 @@ void process_trailers(const char *file, int trim_empty, struct string_list *trai
 	/* Print the lines after the trailers as is */
 	print_lines(outfile, lines, trailer_end, INT_MAX);
 
+	if (in_place)
+		if (rename_tempfile(&trailers_tempfile, file))
+			die_errno(_("could not rename temporary file to %s"), file);
+
 	strbuf_list_free(lines);
 }