CODEWITHSUNDEEP
bashgitdiff
Fabio
Fabio

Reputation: 551

Merge 2 text files with differences marked as conflicts

I'd like to see the complete output of 2 merged files where each difference is marked in the same way as git marks conflicts in the files. The use case is to merge 2 similar configuration files, inspect the merged file and and have visual hints to make evident all differences between the files so that it becomes easy to decide which one to pick.

I have already tried with diff and diff3, but I could only get the differences (with diff) or a fully merged file where only conflicts are marked (with diff3 -m -A file1 file1 file2). I've used git diff and related tools, but they all merge unconflicting changes, instead of marking them as differences.

The running environment would be a bash shell script, therefore it'd be nice to reach the desired output with common linux tools.

Example:

Contents of file1:

environment:
  base_branch: master
  branch: this_is_the_same_for_both_files

Contents of file2:

environment:
  base_branch: a_different_base_branch
  branch: this_is_the_same_for_both_files
  a_new_key: the_new_key_value

Desired output:

environment:
<<<<< file1
  base_branch: master
=====
  base_branch: a_different_base_branch
>>>>> file2
  branch: this_is_the_same_for_both_files
<<<<< file1
=====
  a_new_key: the_new_key_value
>>>>> file2

Upvotes: 2

Views: 865

Answers (1)

Fabio
Fabio

Reputation: 551

Following the suggestions from the comments, I came up with this one liner which seems to solve my issue. I would have liked to use constants for the markers in the sed substitutions, but apparently it's not straightforward to use variables containing \n with sed for mac os.

This code seems to work correctly even in docker alpine:3.8 using diffutils. Other options (brew gnu-sed and similar) might not be easily portable.

diff -D AAAAAAA "${path}" <(echo -n "$decrypted") | \
  sed -e $'s/#ifndef AAAAAAA/<<<<<<< file-on-disk/g' | \
  sed -e $'s/#endif \/\* ! AAAAAAA \*\//=======\\\n>>>>>>> file-from-secret/g' | \

  sed -e $'s/#else \/\* AAAAAAA \*\//=======/g' | \

  sed -e $'s/#ifdef AAAAAAA/<<<<<<< file-on-disk\\\n=======/g' | \
  sed -e $'s/#endif \/\* AAAAAAA \*\//>>>>>>> file-from-secret/g';

Explanation:

diff -D AAAAAAA "${path}" <(echo -n "$decrypted"): outputs a merged text with '#ifdef NAME' diffs. I'm using AAAAAAA as marker name. Diff uses #ifndef AAAAAAA and #endif /* ! AAAAAAA */ to surround text only present in the first file and /#ifdef AAAAAAA and #endif /* AAAAAAA */ to surround text only present in the second. Note the n in the first #ifndef and the ! in the first #endif comment. As all markers are different, it becomes easy to perform substitutions.

sed -e $'s/#endif \/\* ! AAAAAAA \*\//=======\\\n>>>>>>> file-from-secret/g': substitutes the marker with

=======
>>>>>>> file-from-secret

As there is a \n, the substitution string is enclosed with $'' which interprets correctly the new line character. However, the \ needs to be double-escaped.

Upvotes: 2

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