Tests where the RUN-lines/CHECK-ed output refer to line numbers in the test
file are a maintenance burden, as inserting text in the appropriate place
invalidates all the subsequent line numbers.

Lit supports %(line+n) for this, and FileCheck supports [[@LINE+N]].
But many existing tests don't make use of it and still need to be modified.

This commit adds a script that can find line numbers in tests according to a
regex and replace them with the appropriate relative-line reference.
It contains some options to avoid inappropriately rewriting tests where absolute
numbers are appropriate: a "nearby" threshold and a refusal by default to
replace only some matched line numbers.

I've applied it to CodeComplete tests, this proves the concept but also are the
single worst group of tests I've seen in this respect.
These changes are likely to hit merge conflicts, but can be regenerated with:

```
find ../clang/test/CodeCompletion/ -type f | grep -v /Inputs/ | xargs ../llvm/utils/relative_lines.py --verbose --near=20 --pattern='-code-completion-at[ =]%s:(\\d+):' --pattern='requires fix-it: {(\d+):\d+-(\d+):\d+}'
````

As requested in https://reviews.llvm.org/D140044

Fixes https://github.com/llvm/llvm-project/issues/59553

Differential Revision: https://reviews.llvm.org/D140217

Summary:
Make completion behave consistently no matter if it is run at the
start, in the middle or at the end of an identifier that happens to
be a keyword or a macro name. Since completion is often ran on
incomplete identifiers, they may turn into keywords by accident.

For example, we should produce same results for all of these
completion points:

    // ^ is completion point.
    ^class
    cla^ss
    class^

Previously clang produced different results for the last case (as if
the completion point was after a space: `class ^`).

This change also updates some offsets in tests that (unintentionally?)
relied on the old behavior.

Reviewers: sammccall, bkramer, arphaman, aaron.ballman

Reviewed By: sammccall

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D45887

llvm-svn: 330717

Various tests had sprung up over the years which had --check-prefix=ABC on the
RUN line, but "CHECK-ABC:" later on. This happened to work before, but was
strictly incorrect. FileCheck is getting stricter soon though.

Patch by Ron Ofir.

llvm-svn: 188174

the "typed" text, first, then take into account
nested-name-specifiers, name hiding, etc. This means that the
resulting sort is actually alphabetical :)

llvm-svn: 93370

 - This is designed to make it obvious that %clang_cc1 is a "test variable"
   which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
   can be useful to redefine what gets run as 'clang -cc1' (for example, to set
   a default target).

llvm-svn: 91446

llvm-svn: 86432

 - 'for i in $(find . -type f); do sed -e 's#\(RUN:.*[^ ]\) *&& *$#\1#g' $i | FileUpdate $i; done', for the curious.

llvm-svn: 86430

members found in base classes have the same ranking as members found
in derived classes. However, we will introduce an informative note for
members found in base classes, showing (as a nested-name-specifier)
the qualification to name the base class, to make it clear which
members are from bases.
 

llvm-svn: 82586

  -code-completion-at=filename:line:column

which performs code completion at the specified location by truncating
the file at that position and enabling code completion. This approach
makes it possible to run multiple tests from a single test file, and
gives a more natural command-line interface.

llvm-svn: 82571

operators, type specifiers, type names, and nested-name-specifiers.

llvm-svn: 82264