starts-with:
ends-with:

Instead of these options we could support the python regex syntax.

Yes, and an explicit search button instead of the currently implied live reload (or an enter press) would be better UX.
I was thinking of a popup dialog for all extra filters because a big text field for numeric input like size less than doesn't fit well.

A popup for advanced search keeps it simple by default and powerful when needed.

Advanced Search - Where we can have multiple fields together instead of searching by just one field, and changing the field to search again (which does not help cases where multiple filters should be taken into account simultaneously).

Regex support will solve all problems related to names and strings, while the advanced search popup could do this for numeric and complex filters (dates/sizes/etc.)

Advanced Search - Where we can have multiple fields together instead of searching by just one field, and changing the field to search again (which does not help cases where multiple filters should be taken into account simultaneously).

The idea was to have a syntax similar to the search feature on github. E.g. change-type:modified myfile size:>1MB

The idea was to have a syntax similar to the search feature on github. E.g. change-type:modified myfile size:>1MB

I think the dialog would be easier to use without referring to documentation (supported keywords) of any kind, but this works as well.

I think the dialog would be easier to use without referring to documentation

You are right. Would the dialog be open alongside the diff view while sorting or will there be an apply button that closes it? The dialog could also be used to construct the search syntax and insert it into the search bar.

The dialog could also be used to construct the search syntax and insert it into the search bar.

Yes, will help in changing the values faster.

Would the dialog be open alongside the diff view while sorting or will there be an apply button that closes it?

I personally like clicking buttons or pressing keys more than seeing changes live. So I would prefer an apply button that would close it. This will also solve the cluttering problem as it will just add an Advanced... button to the simple search UI.

Whenever a value is given to the dialog for a particular filter, it would append it to the search bar according to the search syntax, and consecutive changes (probably smaller shifts in value), would be quicker to make.

The idea was to have a syntax similar to the search feature on github. E.g. change-type:modified myfile size:>1MB

Just an idea but I think we could also do something like: "change-type: modified size: >1MB" above or below the search bar to see all the applied filters at once, And when hovered over the filter tags it would give a tooltip telling about it. And the user could simply change the filter value or click on the tag to remove or disable it.
Also when typing the filter tag manually it could provide autocomplete which would direct the user towards the correct tags.
I don't know if this could be understood just by words or not but I'll make a mockup as soon as I get free and share it here.

Sounds a bit complex, but yes, maybe a mockup will make your point clearer.

I guess yes, I'll get the mockup done as soon as possible.

If search field already consists filters like change-type:, adding another widget just to show it sounds redundant to me.

If search field already consists filters like change-type:, adding another widget just to show it sounds redundant to me.

That's a thing, but the separated view will make it easier to look at all the selected filter tags and edit them, instead of scrolling left-right to find the tag and the value if there are a lot of filter or a long value or attribute.

Also when typing the filter tag manually it could provide autocomplete which would direct the user towards the correct tags.

That's a good idea.