Finding every merge/commit in git where a file changed

Question

I have a bunch of work that got "lost" in our git repository. i.e. I committed a number of files, and someone did a merge somewhere, that "lost" all my changes. I'm struggling to determine how/where this happened. When I look at the log of changes to my file using this command from this question:

gitk --all -- version.txt

I get the following screenshot:

This file is managed by our build system, and it should contain the string,

1.0.94.0

AT least, based on what I'm seeing in the above screenshot. But in fact, it actually contains the string:

1.0.92.0

In digging through the repository, someone performed a merge, and the merge overwrote version.txt with the contents 1.0.92.0. But that merge did not appear in my gitk output. Is there a way to run gitk (or git) to show me all the merges and commits that modified my file?

It depends on what you know. Does [this](https://stackoverflow.com/questions/47307978/difference-between-different-git-search-commands) help? See also the answer... — Christoph, Dec 06 '17 at 17:56

score 1 · Accepted Answer · answered Dec 06 '17 at 18:57

It's worth trying adding --full-history to your gitk command. gitk runs git log (and sometimes git rev-list) with these gitk-controlled options:

# Start off a git log process and arrange to read its output
proc start_rev_list {view} {
    global startmsecs commitidx viewcomplete curview

[mass snippage]

    if {$vcanopt($view)} {
        set revs [parseviewrevs $view $vrevs($view)]
        if {$revs eq {}} {
            return 0
        }
        set args [concat $vflags($view) $revs]
    } else {
        set args $vorigargs($view)
    }

    if {[catch {
        set fd [open [concat | git log --no-color -z --pretty=raw $show_notes \
                        --parents --boundary $args "--" $files] r]
    } err]} {
        error_popup "[mc "Error executing git log:"] $err"
        return 0
    }

By default, looking at specific files, i.e., when $files is not empty, enables what git log calls History Simplification. I find the documentation here to be somewhat confusing, but in short, without --full-history, Git will prune some merge parents when the parent contains the file in its current format.

Note that --full-history is not included in the options, but one of them is $args, which is at least sometimes set based on $vflags($view), and $vflags may include --full-history.

If you use git log directly, consider adding both --full-history and -m. By default, git log does not look at the diffs of merges. The -m flag causes it to split each merge into one commit-pair per parent (parent-n vs child), and then look at each of those diffs.

I'm not sure if or how this affects gitk since gitk does extra work with git rev-list, but it's possible that adding -m to gitk's options is required as well.

I'm totally cool with a pure git version. When I do 'git -m --full-history version.txt', I get a lot of merges (30+) where the contents of version.txt did not change. I just want the merges where version.txt is different in the merged version from one of the parents..... Is there a way to get this? — John, Dec 06 '17 at 22:55
Unfortunately, the other options for `git log` (`-c` or `--cc`) use *combined diff* and will skip over any merges where the child (the merge) matches *either* of the parents. The `-m` option gets you merges where `version.txt` doesn't match *one* of the parents. That is, you're getting, now, what you're asking for—it's just that many merges include what you're asking for, which suggests you need to ask for something different. — torek, Dec 07 '17 at 00:10

Finding every merge/commit in git where a file changed

1 Answers1