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https://github.com/jbranchaud/til
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39 lines
1.4 KiB
Markdown
39 lines
1.4 KiB
Markdown
# Check If A File Has Changed In A Script
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If I'm at the command line and I want to check if a file has changed, I can run
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`git diff` and see what has changed. If I want to be more specific, I can run
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`git diff README.md` to see if there are changes to that specific file.
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If I'm trying to do this check in a script though, I want the command to clearly
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tell the script _Yes_ or _No_. Usually a script looks for an exit code to
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determine what path to take. But as long as `git diff` runs successfully,
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regardless of whether or not their are changes, it is going to have an
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affirmative exit code of `0`.
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This is why `git diff` offers the `--exit-code` flag.
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> Make the program exit with codes similar to diff(1). That is, it exits with 1
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> if there were differences and 0 means no differences.
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With that in mind, we can wire up a script with `git diff` that takes different
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paths depending on whether or not there are changes.
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```bash
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if ! git diff --exit-code README.md; then
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echo "README.md has changes"
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else
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echo "README.md is clean"
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fi
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```
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We can take this a step further and instead use the `--quiet` flag.
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> Disable all output of the program. Implies --exit-code. Disables execution of
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> external diff helpers whose exit code is not trusted
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This exhibits the same behavior as `--exit-code` and goes the additional step of
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silencing diff output and disabling execution of external diff helpers like
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`delta`.
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See `man git-diff` for more details.
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