Editing an already existing patch file

Question

Is it standard practice to edit a .patch using an editor?

Scenario

I use .patch in Yocto Applications where I want to adapt a few small changes to the repository which I wish to port to my embedded device.

One of the patches is as following (some details removed for brewity):

From 85987c659762939241e4bdd4223e63eb5997b181 Mon Sep 17 00:00:00 2001

OE ships php5 as php

---
 airmar/airmar.php             | 2 +-
 n2kd/n2kd_monitor             | 2 +-
 send-message/format-message   | 2 +-
 util/list-product-information | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/airmar/airmar.php b/airmar/airmar.php
index ccd4b4d..46ed49d 100755
--- a/airmar/airmar.php
+++ b/airmar/airmar.php
@@ -1,4 +1,4 @@
-#!/usr/bin/php5
+#!/usr/bin/env php
 <?php
 if (!is_array($argv))
 {
diff --git a/n2kd/n2kd_monitor b/n2kd/n2kd_monitor
index f8cfd42..4cb4766 100755
--- a/n2kd/n2kd_monitor
+++ b/n2kd/n2kd_monitor
@@ -233,7 +233,7 @@ for (;;)
         open STDIN, '/dev/null' or die "Can't read /dev/null: $!";
         open STDOUT, '>>', $MONITOR_LOGFILE or die "Can't write to $MONITOR_LOGFILE $!";
         open STDERR, '>&STDOUT' or die "Can't dup stdout: $!";
-        exec 'php5', '/usr/local/bin/n2k.php', '-monitor';
+        exec 'php', '/usr/bin/n2k.php', '-monitor';
       }
       if (!$monitor)
       {
diff --git a/send-message/format-message b/send-message/format-message
index 590a815..2d91185 100755
--- a/send-message/format-message
+++ b/send-message/format-message
@@ -1,4 +1,4 @@
-#!/usr/bin/php5
+#!/usr/bin/env php
 <?
 #
 # Format a particular N2K command
diff --git a/util/list-product-information b/util/list-product-information
index d958ae4..a54a0f2 100755
--- a/util/list-product-information
+++ b/util/list-product-information
@@ -1,4 +1,4 @@
-#!/usr/bin/php5
+#!/usr/bin/env php
 <?php
 #
 # A very limited script engine that sends and receives CAN messages.
-- 
2.17.0

This patch simply replaces php5 with env php whereever it occurs.

However, the main code repository changed one of its file where previously there was a shebang for php as follows:

   #!/usr/bin/php5

And now after a few commits it doesn't.

From my understanding, the current patch won't work as it will seek to first find the line number and the content to remove but will through errors since it won't be able to find the above mentioned shebang in the file anymore. (already tried it out)

Possible Way

• A clear way is to clone the repository with the updated code and add the needed shebang (env php and not php5) to the code and use git format-patch -1 to obtain a new patch to be restored.

However this puts a lot of effort and when there are more than a certain number of files changed then this procedure seems to be tedious.

Is it reasonable to edit the patch using an editor (I am quite sure it isn't)? Or are there some git features that help modify the patch directly and not the corresponding file?

Answer 1

There is one other alternative way using quilt refresh. To brief, when using quilt, you will have all the patches copied inside a directory called patches (IMO this is configurable in quiltrc).

File named series inside this patch directory stores all the patch file names. When you apply patch using,

quilt push

or

quilt push -a

you will exit with error. Assume you have 10 patches and 3rd couldn't be applied directly as you have some changes already part of repository.

Then you can call

quilt push -f

which will try to apply all the possible places and stores the line which couldn't applied into .rej file. Example output,

Applying patch patches/0001-To-apply.patch
patching file README.md
Hunk #2 FAILED at 51.
1 out of 2 hunks FAILED -- saving rejects to file README.md.rej

where I have hunks in my README.md file.

Now you can examine the changes which doesn't apply cleanly by comparing original file. In above case between README.md and README.md.rej. You can resolve the failed places and call

quilt refresh

After refresh, your original patch file in patches will be updated with according changes and now you can continue using quilt push or quilt push -a

Note: Yocto by default uses quilt until otherwise change using PATCHTOOL variable.