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freifunk-berlin / falter-builter

build falter images using precompiled openwrt imagebuilders.
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Prevent patch from making the build hang #74

Closed khanku closed 3 years ago

khanku commented 3 years ago

If any of the patches that live under patches/ have already been applied upstream then patch will detect it and ask for user input ("Reversed (or previously applied) patch detected! Assume -R? [n]") effectively preventing the build from continuing until that happens. Note that buildbot is not affected by this (presumably because it closes stdin). Still it would be nice to use patch -f to prevent this. It'd be even better to check whether a patch has been applied already and skip if it has.

Akira25 commented 3 years ago

I just tried that out and found this error to be in effect on snapshot-builds. This issue is on the filename-lenght-patch.

I'm not certain on that -f is a good option here. Is it really safe to force a patch? Would it brake anything if we patch something twice?

On the other hand I have no idea how we could check, if a patch is applied already. @khanku Do you have code for that?

Akira25 commented 3 years ago

I just found -R option. I didn't flash the image, but the build doesn't stop anymore that way.

-R  or  --reverse
          Assume that this patch was created with the old and new files swapped.  (Yes, I'm afraid that does  happen  occasion‐
          ally,  human nature being what it is.)  patch attempts to swap each hunk around before applying it.  Rejects come out
          in the swapped format.  The -R option does not work with ed diff scripts because there is too little  information  to
          reconstruct the reverse operation.

          If the first hunk of a patch fails, patch reverses the hunk to see if it can be applied that way.  If it can, you are
          asked if you want to have the -R option set.  If it can't, the patch continues to be applied normally.   (Note:  this
          method  cannot  detect  a reversed patch if it is a normal diff and if the first command is an append (i.e. it should
          have been a delete) since appends always succeed, due to the fact that a null  context  matches  anywhere.   Luckily,
          most  patches  add  or change lines rather than delete them, so most reversed normal diffs begin with a delete, which
          fails, triggering the heuristic.)
khanku commented 3 years ago

I would argue that -f is safe in the sense that it will work non-interactively but still fail if a patch cannot be applied. Regarding the combination of -f and -R: I agree, see https://github.com/Freifunk-Spalter/builter/pull/75

Akira25 commented 3 years ago

Fixed by #75