Differences

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--- git_ignore [2018/06/04 11:45] – [Four levels of ignoring files] rpjday
+++ git_ignore [2019/02/22 18:18] (current) – [Debugging gitignore files] rpjday
@@ Line 1: / Line 1: @@
 ===== Overview =====
-How to identify untracked files that Git should intentionally ignore; files already tracked by Git are not affected.
+How to identify untracked files that Git should intentionally ignore when running numerous commands, such as ''git add -u'', ''git status'', ''git clean'' and many more.
 Some links:
@@ Line 8: / Line 8: @@
   * [[https://www.gitignore.io|Generate a gitignore file]]
-===== Four levels of ignoring files =====
+===== Introductory .gitignore =====
+==== Basic .gitignore file ====
+Excerpts from the Linux kernel source top-level ''.gitignore'' file, which forces ignoring of all these file patterns //recursively//:
+<code>
+.*                               [all hidden files/directories]
+*.a
+*.asn1.[ch]
+*.bz2
+*.c.[012]*.*
+*.dt.yaml
+*.dtb
+*.dtb.S
+*.dwo
+*.elf
+*.gz
+*.ko
+...
+Module.symvers                    [specific filename]
+...
+#
+# Top-level generic files
+#
+/tags
+/TAGS
+/linux
+/vmlinux
+/vmlinux.32
+/vmlinux-gdb.py
+...
+/debian/                           [top-level directory only]
+...
+#
+# Exceptions: git files that we don't want to ignore even if they are dot-files
+#
+!.gitignore
+!.mailmap
+!.cocciconfig
+!.clang-format
+...
+#
+# Generated include files
+#
+include/config
+include/generated
+include/ksym
+arch/*/include/generated
+...
+</code>
+==== Recursive .gitignore ====
+Subdirectories can have more specific ''.gitignore'' files that take precedence in those subdirectories. For the Linux kernel source, the top-level directory ''scripts/'' has the ''.gitignore'' file:
+<code>
+#
+# Generated files
+#
+bin2c
+conmakehash
+kallsyms
+pnmtologo
+unifdef
+recordmcount
+sortextable
+asn1_compiler
+extract-cert
+sign-file
+insert-sys-cert
+</code>
+The Linux kernel source repo has over 200 ''.gitignore'' files.
+===== Advanced ignoring =====
+==== Four levels of ignoring files ====
 Each line in a gitignore/exclude file specifies a pattern. When deciding whether to ignore a path, Git normally checks gitignore patterns from multiple sources, with the following order of precedence, from highest to lowest (within one level of precedence, the last matching pattern decides the outcome):
@@ Line 17: / Line 93: @@
   * Patterns read from the file specified by the configuration variable ''core.excludesFile'' (possibly ''~/.my_ignorefile'').
-===== Rationale for different levels of gitignore files =====
+==== Rationale for different levels of gitignore files ====
   * Patterns which should be version-controlled and distributed to other repositories via clone (i.e., files that //all// developers will want to ignore) should go into a ''.gitignore'' file that comes with the repository.
@@ Line 23: / Line 99: @@
   * Patterns which a user wants Git to ignore in //all// situations (e.g., backup or temporary files generated by the user’s editor of choice) generally go into a file specified by ''core.excludesFile'' in the user’s ''~/.gitconfig''.
-===== Debugging gitignore files =====
+<code>
+$ git config --global core.excludesfile ~/.my_ignorefile
+</code>
+==== Debugging gitignore files ====
 <code>
 $ man git-check-ignore
 </code>
+===== gitignore gotchas =====
+  * Since ''.gitignore'' is a versioned file, checking out a different commit might result in a different ''.gitignore'' file, causing unexpected behaviour.