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

On 2016-01-06 at 20:02:23 +0100, Eric Sunshine [off-list ref] wrote:

On Wed, Jan 6, 2016 at 8:34 AM, Tobias Klauser
[off-list ref] wrote:

quoted

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...

quoted

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!