61 lines
3 KiB
JavaScript
61 lines
3 KiB
JavaScript
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function swapPrefix(fileName) {
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if (fileName === undefined || fileName === '/dev/null') {
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return fileName;
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}
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if (fileName.startsWith('a/')) {
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return 'b/' + fileName.slice(2);
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}
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if (fileName.startsWith('b/')) {
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return 'a/' + fileName.slice(2);
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}
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return fileName;
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}
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export function reversePatch(structuredPatch) {
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if (Array.isArray(structuredPatch)) {
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// (See comment in unixToWin for why we need the pointless-looking anonymous function here)
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return structuredPatch.map(patch => reversePatch(patch)).reverse();
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}
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const reversed = Object.assign(Object.assign({}, structuredPatch), { oldFileName: structuredPatch.isGit ? swapPrefix(structuredPatch.newFileName) : structuredPatch.newFileName, oldHeader: structuredPatch.newHeader, newFileName: structuredPatch.isGit ? swapPrefix(structuredPatch.oldFileName) : structuredPatch.oldFileName, newHeader: structuredPatch.oldHeader, oldMode: structuredPatch.newMode, newMode: structuredPatch.oldMode, isCreate: structuredPatch.isDelete, isDelete: structuredPatch.isCreate, hunks: structuredPatch.hunks.map(hunk => {
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return {
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oldLines: hunk.newLines,
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oldStart: hunk.newStart,
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newLines: hunk.oldLines,
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newStart: hunk.oldStart,
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lines: hunk.lines.map(l => {
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if (l.startsWith('-')) {
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return `+${l.slice(1)}`;
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}
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if (l.startsWith('+')) {
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return `-${l.slice(1)}`;
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}
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return l;
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})
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};
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}) });
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if (structuredPatch.isCopy) {
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// Reversing a copy means deleting the file that was created by the copy.
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// The "old" file in the reversed patch is the copy destination (which
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// exists and should be removed), and the "new" file is /dev/null.
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//
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// Note: we clear the hunks because the original copy's hunks describe
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// the diff between the source and destination, not the full content of
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// the destination file, so they can't be meaningfully reversed into a
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// deletion hunk. This means the resulting patch is not something
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// `git apply` will accept (it requires deletion patches to include a
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// hunk removing every line). Producing a correct deletion hunk would
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// require knowing the full content of the copy destination, which we
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// don't have. Consumers that need a `git apply`-compatible patch will
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// need to resolve the full file content themselves.
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reversed.newFileName = '/dev/null';
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reversed.newHeader = undefined;
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reversed.isDelete = true;
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delete reversed.isCreate;
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delete reversed.isCopy;
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delete reversed.isRename;
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reversed.hunks = [];
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}
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// Reversing a rename is just a rename in the opposite direction;
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// isRename stays set and the filenames are already swapped above.
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return reversed;
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}
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