git status shows files in untracked list though they are in .gitignore and removed from the cache

Question

~/rails_projects/sample_app2 $ git branch
* master

~/rails_projects/sample_app2$ cat .gitignore
# See https://help.github.com/articles/ignoring-files for more about ignoring files.
#
# If you find yourself ignoring temporary files generated by your text editor
# or operating system, you probably want to add a global ignore instead:
#   git config --global core.excludesfile '~/.gitignore_global'

# Ignore bundler config.
/.bundle

# Ignore the default SQLite database.
/db/*.sqlite3
/db/*.sqlite3-journal

# Ignore all logfiles and tempfiles.
/log/*.log
/tmp

# Ignore other unneeded files.
database.yml
doc/
.*.s[a-w][a-z]  #all swap files
.*.*.s[a-w][a-z]
.*.*.*.s[a-w][a-z]
*~
.project
.DS_Store
.idea
.secret

~/rails_projects/sample_app2$ touch .gitignore.swp

~/rails_projects/sample_app2$ git status
# On branch master
# Your branch is ahead of 'origin/master' by 15 commits.
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   .gitignore.swp
nothing added to commit but untracked files present (use "git add" to track)

~/rails_projects/sample_app2$ git add .
~/rails_projects/sample_app2$ git commit -m "Add swap file"
[master 364570c] Add swap file
 0 files changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 .gitignore.swp

~/rails_projects/sample_app2$ git rm --cached .gitignore.swp
rm '.gitignore.swp'

~/rails_projects/sample_app2$ git status
# On branch master
# Your branch is ahead of 'origin/master' by 16 commits.
#
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   deleted:    .gitignore.swp
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   .gitignore.swp


~/rails_projects/sample_app2$ git commit -m "Remove swap file"
[master 485217f] Remove swap file
 0 files changed, 0 insertions(+), 0 deletions(-)
 delete mode 100644 .gitignore.swp

~/rails_projects/sample_app2$ git status
# On branch master
# Your branch is ahead of 'origin/master' by 17 commits.
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   .gitignore.swp
nothing added to commit but untracked files present (use "git add" to track)

~/rails_projects/sample_app2$ $ git add .

~/rails_projects/sample_app2$ git commit -m "Trying NOT to add swap files"
[master d743282] Trying NOT to add swap files
 0 files changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 .gitignore.swp

And on and on and on. Swap files keep showing up in the untracked files list when I do:

$ git status

Therefore when I do my next commit, the swap files get added to the files that git is tracking. How do I make git ignore all swap files?

This seems like such a common problem that there should be a command:

$ git ignore --all-swap-files

Response to one of the comments:

~/rails_projects$ mkdir test_gitignore
~/rails_projects$ cd test_gitignore/
~/rails_projects/test_gitignore$ touch .gitignore
~/rails_projects/test_gitignore$ echo '.*.s[a-w][a-z]' > .gitignore
~/rails_projects/test_gitignore$ git init
Initialized empty Git repository in /Users/7stud/rails_projects/test_gitignore/.git/
~/rails_projects/test_gitignore$ touch file1.txt .file1.swp
~/rails_projects/test_gitignore$ mkdir subdir
~/rails_projects/test_gitignore$ touch subdir/.file2.swp
~/rails_projects/test_gitignore$ ls -al
total 8
drwxr-xr-x   7 7stud  staff  238 Sep 14 10:41 .
drwxr-xr-x  19 7stud  staff  646 Sep 14 10:38 ..
-rw-r--r--   1 7stud  staff    0 Sep 14 10:40 .file1.swp
drwxr-xr-x  10 7stud  staff  340 Sep 14 10:40 .git
-rw-r--r--   1 7stud  staff   15 Sep 14 10:40 .gitignore
-rw-r--r--   1 7stud  staff    0 Sep 14 10:40 file1.txt
drwxr-xr-x   3 7stud  staff  102 Sep 14 10:41 subdir
~/rails_projects/test_gitignore$ ls -al subdir
total 0
drwxr-xr-x  3 7stud  staff  102 Sep 14 10:41 .
drwxr-xr-x  7 7stud  staff  238 Sep 14 10:41 ..
-rw-r--r--  1 7stud  staff    0 Sep 14 10:41 .file2.swp

~/rails_projects/test_gitignore$ git status
# On branch master
#
# Initial commit
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#   .gitignore
#   file1.txt
nothing added to commit but untracked files present (use "git add" to track)
~/rails_projects/test_gitignore$ 

Answer 1

Here is what is happening: Your .gitignore rules have extra spaces at the end of them. Git treats each entry within the gitignore as a ignore rule in entirety, it is precisely for the same reason you shouldn't have that comment in your gitignore - the pattern changes.

So, .*.s[a-w][a-z], though looks all right visibly in your .gitignore, happens to be the string ".*.s[a-w][a-z] "

Hence git ignore is unable to match the swap files.

As an aside, you can do away with the three swap ingore rules and use a single one instead

*.s[a-w][a-z]

And here is a sample python snippet to test what exactly the new pattern is matching (or not matching)

In [1]: import fnmatch

In [2]: pattern = "*.s[a-w][a-z]"

In [3]: filenames = [".file.swp", "folder/.file.swp", "folder/subfolder/.file.swp", ".f.i.l.e.swp", "folder/.f.i.l.e.swp"]

In [4]: for filename in filenames:
   ...:     print filename, fnmatch.fnmatch(filename, pattern)
   ...:     
.file.swp True
folder/.file.swp True
folder/subfolder/.file.swp True
.f.i.l.e.swp True
folder/.f.i.l.e.swp True

In [5]: pattern = ".*.s[a-w][a-z]"

In [6]: for filename in filenames:
    print filename, fnmatch.fnmatch(filename, pattern)
   ...:     
.file.swp True
folder/.file.swp False
folder/subfolder/.file.swp False
.f.i.l.e.swp True
folder/.f.i.l.e.swp False

Answer 2

The problem is quite simple, it's the line

.*.s[a-w][a-z]  #all swap files

In a .gitignore file, comments can only be at the start of the line. Change this to

#all swap files
.*.s[a-w][a-z]

and it will work as intended:

$ /bin/echo -e '.*.s[a-w][a-z] # swap' > .gitignore 
$ touch .gitignore.swp
$ touch .x.swp
$ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   .gitignore

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        .gitignore.swp
        .x.swp

no changes added to commit (use "git add" and/or "git commit -a")
$ /bin/echo -e '.*.s[a-w][a-z]\n# swap' > .gitignore 
$ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        modified:   .gitignore

no changes added to commit (use "git add" and/or "git commit -a")