298 lines
14 KiB
Python
298 lines
14 KiB
Python
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# SOURCE: https://github.com/spyder-ide/three-merge/blob/master/three_merge/merge.py
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from typing import Optional
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from diff_match_patch import diff_match_patch
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# Constants
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DIFFER = diff_match_patch()
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DIFFER.Diff_Timeout = 0.1
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DIFFER.Diff_EditCost = 4
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PRESERVED = 0
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DELETION = -1
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ADDITION = 1
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def merge(
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source: Optional[str], target: Optional[str], base: Optional[str]
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) -> Optional[str]:
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if source is None or target is None or base is None:
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return None
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diff1_l = DIFFER.diff_main(base, source)
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diff2_l = DIFFER.diff_main(base, target)
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DIFFER.diff_cleanupEfficiency(diff1_l)
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DIFFER.diff_cleanupEfficiency(diff2_l)
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diff1 = iter(diff1_l)
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diff2 = iter(diff2_l)
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composed_text = []
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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prev_source_text = ""
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prev_target_text = ""
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while source is not None and target is not None:
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source_status, source_text = source
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target_status, target_text = target
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if source_status == PRESERVED and target_status == PRESERVED:
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# Base is preserved for both source and target
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if len(source_text) > len(target_text):
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# Addition performed by target
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advance = True
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composed_text.append(target_text)
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tempdiff = DIFFER.diff_main(target_text, source_text)
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_, invariant = tempdiff[1]
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# _, (_, invariant) = DIFFER.diff_main(target_text, source_text)
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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while invariant != "" and target is not None:
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# Apply target changes until invariant is preserved
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# target = next(diff2, None)
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target_status, target_text = target
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if target_status == DELETION:
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if len(target_text) > len(invariant):
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target_text = target_text[len(invariant) :]
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invariant = ""
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target = (target_status, target_text) # type: ignore
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else:
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invariant = invariant[len(target_text) :]
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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elif target_status == ADDITION:
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composed_text.append(target_text)
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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else:
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# Recompute invariant and advance source
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if len(invariant) > len(target_text):
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assert invariant[: len(target_text)] == target_text
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source = (source_status, invariant[len(target_text) :]) # type: ignore
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composed_text.append(target_text)
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invariant = ""
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advance = False
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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else:
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target_text = target_text[len(invariant) :]
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composed_text.append(invariant)
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invariant = ""
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target = (target_status, target_text) # type: ignore
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if advance:
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prev_source_text = source[1] # type: ignore
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source = next(diff1, None) # type: ignore
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elif len(source_text) < len(target_text):
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# Addition performed by source
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advance = True
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composed_text.append(source_text)
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tempdiff = DIFFER.diff_main(target_text, source_text)
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_, invariant = tempdiff[1] if len(tempdiff) > 1 else tempdiff[0]
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# _, (_, invariant) = DIFFER.diff_main(source_text, target_text)
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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while invariant != "" and target is not None and source is not None:
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# Apply source changes until invariant is preserved
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source_status, source_text = source
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if source_status == DELETION:
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if len(source_text) > len(invariant):
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source_text = source_text[len(invariant) :]
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invariant = ""
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source = (source_status, source_text) # type: ignore
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else:
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invariant = invariant[len(source_text) :]
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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elif source_status == ADDITION:
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composed_text.append(source_text)
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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else:
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# Recompute invariant and advance source
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# invariant = invariant[:len(source_text)]
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if len(invariant) > len(source_text):
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assert invariant[: len(source_text)] == source_text
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target = (target_status, invariant[len(source_text) :]) # type: ignore
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composed_text.append(source_text)
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invariant = ""
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advance = False
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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else:
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source_text = source_text[len(invariant) :]
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composed_text.append(invariant)
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invariant = ""
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source = (source_status, source_text) # type: ignore
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if advance:
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prev_target_text = target[1] # type: ignore
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target = next(diff2, None) # type: ignore
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else:
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# Source and target are equal
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composed_text.append(source_text)
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prev_source_text = source[1]
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prev_target_text = target[1]
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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elif source_status == ADDITION and target_status == PRESERVED:
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# Source is adding text
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composed_text.append(source_text)
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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elif source_status == PRESERVED and target_status == ADDITION:
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# Target is adding text
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composed_text.append(target_text)
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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elif source_status == DELETION and target_status == PRESERVED:
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if len(target_text) > len(source_text):
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# Take target text, remove the corresponding part from source
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target_text = target_text[len(source_text) :]
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# composed_text.append(target_text)
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# source = diff1.pop(0)
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target = (target_status, target_text) # type: ignore
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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elif len(target_text) <= len(source_text):
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source_text = source_text[len(target_text) :]
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source = (source_status, source_text) # type: ignore
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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elif source_status == PRESERVED and target_status == DELETION:
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if len(source_text) > len(target_text):
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# Take source text, remove the corresponding part from target
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source_text = source_text[len(target_text) :]
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source = (source_status, source_text) # type: ignore
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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elif len(source_text) <= len(target_text):
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# Advance to next source
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target_text = target_text[len(source_text) :]
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target = (target_status, target_text) # type: ignore
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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elif source_status == DELETION and target_status == ADDITION:
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# Merge conflict
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# Err on the side of deletion. Do not add anything
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# composed_text.append("<<<<<<< ++ {0} ".format(target_text))
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# composed_text.append("======= -- {0} ".format(source_text))
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# composed_text.append(">>>>>>>")
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prev_source_text = source[1]
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prev_target_text = target[1]
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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if target is not None:
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target_status, target_text = target
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if target_text.startswith(source_text):
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target_text = target_text[len(source_text) :]
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target = (target_status, target_text) # type: ignore
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elif source_status == ADDITION and target_status == DELETION:
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# Merge conflict
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# Err on the side of deletion. Do not add anything
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# composed_text.append("<<<<<<< ++ {0} ".format(source_text))
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# composed_text.append("======= -- {0} ".format(target_text))
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# composed_text.append(">>>>>>>")
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prev_source_text = source[1]
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prev_target_text = target[1]
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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if source is not None:
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source_status, source_text = source
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if source_text.startswith(target_text):
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source_text = source_text[len(target_text) :]
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source = (source_status, source_text) # type: ignore
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elif source_status == ADDITION and target_status == ADDITION:
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# Possible merge conflict
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if len(source_text) >= len(target_text):
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if source_text.startswith(target_text):
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composed_text.append(source_text)
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else:
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# Merge conflict
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# Insert text that has highest distance from original
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# we assume original is last operation
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source_dist = DIFFER.diff_levenshtein(
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DIFFER.diff_main(source_text, prev_source_text)
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)
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target_dist = DIFFER.diff_levenshtein(
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DIFFER.diff_main(target_text, prev_target_text)
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)
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if source_dist > target_dist:
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composed_text.append(source_text)
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else:
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composed_text.append(target_text)
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else:
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if target_text.startswith(source_text):
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composed_text.append(target_text)
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else:
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# Merge conflict
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# Insert text that has highest distance from original
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source_dist = DIFFER.diff_levenshtein(
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DIFFER.diff_main(source_text, prev_source_text)
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)
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target_dist = DIFFER.diff_levenshtein(
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DIFFER.diff_main(target_text, prev_target_text)
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)
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if source_dist > target_dist:
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composed_text.append(source_text)
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else:
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composed_text.append(target_text)
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prev_source_text = source[1]
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prev_target_text = target[1]
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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elif source_status == DELETION and target_status == DELETION:
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# Possible merge conflict
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merge_conflict = False
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if len(source_text) > len(target_text):
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if source_text.startswith(target_text):
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# Peek target to delete preserved text
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source_text = source_text[len(target_text) :]
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source = (source_status, source_text) # type: ignore
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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else:
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merge_conflict = True
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elif len(target_text) > len(source_text):
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if target_text.startswith(source_text):
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target_text = target_text[len(source_text) :]
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target = (target_status, target_text) # type: ignore
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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else:
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merge_conflict = True
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else:
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if target_text == source_text:
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# Both source and target remove the same text
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prev_source_text = source[1]
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prev_target_text = target[1]
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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else:
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merge_conflict = True
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# Don't handle double deletion scenario
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if merge_conflict:
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source = next(diff1, None) # type: ignore
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target = next(diff2, None) # type: ignore
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# composed_text.append("<<<<<<< -- {0} ".format(source_text))
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# composed_text.append("======= -- {0} ".format(target_text))
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# composed_text.append(">>>>>>>")
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while source is not None:
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source_status, source_text = source
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# assert source_status == ADDITION or source_status == PRESERVED
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if source_status == ADDITION:
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composed_text.append(source_text)
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prev_source_text = source[1]
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source = next(diff1, None) # type: ignore
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while target is not None:
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target_status, target_text = target
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# assert target_status == ADDITION or source_status == PRESERVED
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if target_status == ADDITION:
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composed_text.append(target_text)
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prev_target_text = target[1]
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target = next(diff2, None) # type: ignore
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return "".join(composed_text)
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