[bug-diffutils] bug#44379: bug#44379: File name affects patch patched file regardless of diff

[Andreas Grünbacher]

Am So., 1. Nov. 2020 um 23:36 Uhr schrieb Michael Partridge <mcp292@nau.edu>:
> Reproduce with:
>
> diff -u driver.c.master driver.c > d.diff
> patch < d.diff
>
> driver.c is patched instead of the intended driver.c.master. If I change the 
> name to master_driver.c it works as intended.

Unfortunately, patch has no way of knowing what you mean. The filename
selection algorithm is described here:

https://www.gnu.org/software/diffutils/manual/html_node/Multiple-Patches.html

> The use case:
> When I want to merge a couple lines of changes from another git branch, I 
> sometimes rename the file in the master branch by appending .master then 
> checkout the file that has some of the changes I want. From there I run the 
> diffs as seen above and manually edit the diff file to achieve the exact 
> edits I want before patching.

Since you're in a git workflow already, you may be better served by
"git diff", "git add -p", "git reset", and similar commands.
Alternatively, use diff's --label option.

Andreas