pretty: find pretty formats case-insensitively

User-defined pretty formats are stored in config, which is meant to use case-insensitive matching for names as noted in config.txt's 'Syntax' section: All the other lines [...] are recognized as setting variables, in the form 'name = value' [...]. The variable names are case-insensitive, [...]. When a user specifies one of their format aliases with an uppercase in it, however, it is not found. $ git config pretty.testAlias %h $ git config --list | grep pretty pretty.testalias=%h $ git log --format=testAlias -1 fatal: invalid --pretty format: testAlias $ git log --format=testalias -1 3c2a3fdc38 This is true whether the name in the config file uses any uppercase characters or not. Use case-insensitive comparisons when identifying format aliases. Co-authored-by: Jeff King <peff@peff.net> Signed-off-by: Brian Lyles <brianmlyles@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>