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How can I grep Git commits for a certain word?

In a Git code repository I want to list all commits that contain a certain word. I tried this

git log -p | grep --context=4 "word"

but it does not necessarily give me back the filename (unless it's less that five lines away from the word I searched for. I also tried

git grep "word"

but it gives me only present files and not the history.

How do I search the entire history, so I can follow changes on a particular word? I intend to search my codebase for occurrences of word to track down changes (search in files history).

Solution

  • If you want to find all commits where the commit message contains a given word, use

    git log --grep=word

    If you want to find all commits where "word" was added or removed in the file contents (to be more exact: where the number of occurrences of "word" changed), i.e., search the commit contents, use a so-called 'pickaxe' search with

    git log -Sword

    In modern Git there is also

    git log -Gword

    to look for differences whose added or removed line matches "word" (also commit contents).

    A few things to note:

    • -G by default accepts a regex, while -S accepts a string, but it can be modified to accept regexes using the --pickaxe-regex.
    • -S finds commits where the number of occurrences of "word" changed, while -G finds commits where "word" appears in the diff.
    • This means that -S<regex> --pickaxe-regex and -G<regex> do not do exactly the same thing.

    The git diff documentation has a nice explanation of the difference:

    To illustrate the difference between -S<regex> --pickaxe-regex and -G<regex>, consider a commit with the following diff in the same file:

    +    return frotz(nitfol, two->ptr, 1, 0);
...
-    hit = frotz(nitfol, mf2.ptr, 1, 0);

    While git log -G"frotz\(nitfol" will show this commit, git log -S"frotz\(nitfol" --pickaxe-regex will not (because the number of occurrences of that string did not change).

    This will show the commits containing the search terms, but if you want to see the actual changes in those commits instead you can use --patch:

    git log -G"searchTerm" --patch

    This can then be piped to grep to isolate the output just to display commit diff lines with that search term. A common use-case is to display diff lines with that search term in commits since and including a given commit - 3b5ab0f2a1 in this example - like so:

    git log 3b5ab0f2a1^.. -G"searchTerm" --patch | grep searchTerm